diff --git a/CMakeLists.txt b/CMakeLists.txt
index f8fd5b7637..476164b845 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -7,6 +7,40 @@ else()
   cmake_minimum_required(VERSION 3.2)
 endif()
 
+
+# Passing of variables to vcpkg
+#
+# vcpkg runs cmake scripts in an isolated environment, see this for details:
+# https://github.com/Microsoft/vcpkg/issues/3712
+#
+# Here's how this works and how we work around this issue:
+#
+# 1. This file (CMakeLists.txt) runs first and is authoritative. It is the one
+#    that reads the environment, sets variables and sets a default value.
+# 2. It writes the contents of the variables to 
+#    $CMAKE_CURRENT_BINARY_DIR/_env/$VARNAME
+# 3. hifi_vcpkg.py takes the _env directory, and copies it to the vcpkg dir.
+#    This solves the issue of CMakeLists.txt not knowing where the vcpkg dir is.
+# 4. cmake/ports/*/portfile.cmake does know where the vcpkg dir is, and can
+#    read the _env that was copied there to obtain the variable's name.
+#
+# To ensure no old data could be accidentally read, the _env directories are
+# deleted on each execution and fully recreated.
+
+# Ensure nothing is kept from any previous run
+file(REMOVE_RECURSE "${CMAKE_CURRENT_BINARY_DIR}/_env")
+file(MAKE_DIRECTORY "${CMAKE_CURRENT_BINARY_DIR}/_env")
+
+# Base URL for externally downloaded files
+set(EXTERNAL_BUILD_ASSETS "https://athena-public.s3.amazonaws.com")
+
+if( DEFINED ENV{EXTERNAL_BUILD_ASSETS} )
+    set(EXTERNAL_BUILD_ASSETS "$ENV{EXTERNAL_BUILD_ASSETS}")
+endif()
+
+file(WRITE "${CMAKE_CURRENT_BINARY_DIR}/_env/EXTERNAL_BUILD_ASSETS.txt" "${EXTERNAL_BUILD_ASSETS}")
+MESSAGE(STATUS "EXTERNAL_BUILD_ASSETS: ${EXTERNAL_BUILD_ASSETS}")
+
 include("${CMAKE_CURRENT_SOURCE_DIR}/cmake/macros/TargetPython.cmake")
 target_python()
 
diff --git a/cmake/externals/GifCreator/CMakeLists.txt b/cmake/externals/GifCreator/CMakeLists.txt
index 094f5612a9..bacfefd48b 100644
--- a/cmake/externals/GifCreator/CMakeLists.txt
+++ b/cmake/externals/GifCreator/CMakeLists.txt
@@ -3,7 +3,7 @@ set(EXTERNAL_NAME GifCreator)
 include(ExternalProject)
 ExternalProject_Add(
   ${EXTERNAL_NAME}
-  URL https://public.highfidelity.com/dependencies/GifCreator.zip
+  URL "${EXTERNAL_BUILD_ASSETS}/dependencies/GifCreator.zip"
   URL_MD5 8ac8ef5196f47c658dce784df5ecdb70
   CONFIGURE_COMMAND ""
   BUILD_COMMAND ""
@@ -17,4 +17,4 @@ set_target_properties(${EXTERNAL_NAME} PROPERTIES FOLDER "hidden/externals")
 ExternalProject_Get_Property(${EXTERNAL_NAME} INSTALL_DIR)
 
 string(TOUPPER ${EXTERNAL_NAME} EXTERNAL_NAME_UPPER)
-set(${EXTERNAL_NAME_UPPER}_INCLUDE_DIRS ${INSTALL_DIR}/src/${EXTERNAL_NAME} CACHE PATH "List of GifCreator include directories")
\ No newline at end of file
+set(${EXTERNAL_NAME_UPPER}_INCLUDE_DIRS ${INSTALL_DIR}/src/${EXTERNAL_NAME} CACHE PATH "List of GifCreator include directories")
diff --git a/cmake/externals/LibOVR/CMakeLists.txt b/cmake/externals/LibOVR/CMakeLists.txt
index 53c4c2976c..872d0e5fef 100644
--- a/cmake/externals/LibOVR/CMakeLists.txt
+++ b/cmake/externals/LibOVR/CMakeLists.txt
@@ -17,7 +17,7 @@ if (WIN32)
 
   ExternalProject_Add(
     ${EXTERNAL_NAME}
-    URL https://hifi-public.s3.amazonaws.com/dependencies/ovr_sdk_win_1.35.0.zip
+    URL "${EXTERNAL_BUILD_ASSETS}/dependencies/ovr_sdk_win_1.35.0.zip"
     URL_MD5 1e3e8b2101387af07ff9c841d0ea285e
     CMAKE_ARGS -DCMAKE_INSTALL_PREFIX:PATH=<INSTALL_DIR>
     PATCH_COMMAND ${CMAKE_COMMAND} -E copy "${CMAKE_CURRENT_SOURCE_DIR}/LibOVRCMakeLists.txt" <SOURCE_DIR>/CMakeLists.txt
@@ -38,7 +38,7 @@ elseif(APPLE)
   
   ExternalProject_Add(
     ${EXTERNAL_NAME}
-    URL https://public.highfidelity.com/dependencies/ovr_sdk_macos_0.5.0.1.tar.gz
+    URL "${EXTERNAL_BUILD_ASSETS}/dependencies/ovr_sdk_macos_0.5.0.1.tar.gz"
     URL_MD5 0a0785a04fb285f64f62267388344ad6
     CONFIGURE_COMMAND ""
     BUILD_COMMAND ""
diff --git a/cmake/externals/LibOVRPlatform/CMakeLists.txt b/cmake/externals/LibOVRPlatform/CMakeLists.txt
index adf89823f2..40e6ae123c 100644
--- a/cmake/externals/LibOVRPlatform/CMakeLists.txt
+++ b/cmake/externals/LibOVRPlatform/CMakeLists.txt
@@ -9,7 +9,7 @@ if (WIN32)
 
   ExternalProject_Add(
     ${EXTERNAL_NAME}
-    URL https://public.highfidelity.com/dependencies/OVRPlatformSDK_v1.10.0.zip
+    URL "${EXTERNAL_BUILD_ASSETS}/dependencies/OVRPlatformSDK_v1.10.0.zip"
     URL_MD5 e6c8264af16d904e6506acd5172fa0a9
     CONFIGURE_COMMAND ""
     BUILD_COMMAND ""
diff --git a/cmake/externals/crashpad/CMakeLists.txt b/cmake/externals/crashpad/CMakeLists.txt
index 34348b6418..e519ead0ee 100644
--- a/cmake/externals/crashpad/CMakeLists.txt
+++ b/cmake/externals/crashpad/CMakeLists.txt
@@ -6,7 +6,7 @@ string(TOUPPER ${EXTERNAL_NAME} EXTERNAL_NAME_UPPER)
 if (WIN32)
     ExternalProject_Add(
       ${EXTERNAL_NAME}
-      URL https://public.highfidelity.com/dependencies/crashpad_062317.1.zip
+      URL "${EXTERNAL_BUILD_ASSETS}/dependencies/crashpad_062317.1.zip"
       URL_MD5 9c84b77f5f23daf939da1371825ed2b1
       CONFIGURE_COMMAND ""
       BUILD_COMMAND ""
@@ -25,7 +25,7 @@ if (WIN32)
 elseif (APPLE)
   ExternalProject_Add(
     ${EXTERNAL_NAME}
-    URL https://public.highfidelity.com/dependencies/crashpad_mac_070318.zip
+    URL "${EXTERNAL_BUILD_ASSETS}/dependencies/crashpad_mac_070318.zip"
     URL_MD5 ba1501dc163591ac2d1be74946967e2a
     CONFIGURE_COMMAND ""
     BUILD_COMMAND ""
diff --git a/cmake/externals/glad32es/CMakeLists.txt b/cmake/externals/glad32es/CMakeLists.txt
index 04000b4cfe..8487e5aaaf 100644
--- a/cmake/externals/glad32es/CMakeLists.txt
+++ b/cmake/externals/glad32es/CMakeLists.txt
@@ -5,7 +5,7 @@ include(SelectLibraryConfigurations)
 
 ExternalProject_Add(
   ${EXTERNAL_NAME}
-  URL https://public.highfidelity.com/dependencies/glad/glad32es.zip
+  URL "${EXTERNAL_BUILD_ASSETS}/dependencies/glad/glad32es.zip"
   URL_MD5 6a641d8c49dee4c895fa59315f5682a6
   CONFIGURE_COMMAND CMAKE_ARGS -DCMAKE_BUILD_TYPE=${CMAKE_BUILD_TYPE} -DCMAKE_INSTALL_PREFIX:PATH=<INSTALL_DIR> -DCMAKE_POSITION_INDEPENDENT_CODE=ON
   LOG_DOWNLOAD 1
diff --git a/cmake/externals/glad41/CMakeLists.txt b/cmake/externals/glad41/CMakeLists.txt
index 0c99a03025..76382dd05d 100644
--- a/cmake/externals/glad41/CMakeLists.txt
+++ b/cmake/externals/glad41/CMakeLists.txt
@@ -5,7 +5,7 @@ include(SelectLibraryConfigurations)
 
 ExternalProject_Add(
   ${EXTERNAL_NAME}
-  URL https://public.highfidelity.com/dependencies/glad/glad41.zip
+  URL "${EXTERNAL_BUILD_ASSETS}/dependencies/glad/glad41.zip"
   URL_MD5 1324eeec33abe91e67d19ae551ba624d
   CONFIGURE_COMMAND CMAKE_ARGS -DCMAKE_BUILD_TYPE=${CMAKE_BUILD_TYPE} -DCMAKE_INSTALL_PREFIX:PATH=<INSTALL_DIR> -DCMAKE_POSITION_INDEPENDENT_CODE=ON
   LOG_DOWNLOAD 1
diff --git a/cmake/externals/glad45/CMakeLists.txt b/cmake/externals/glad45/CMakeLists.txt
index 112f6f3592..477a5f79d5 100644
--- a/cmake/externals/glad45/CMakeLists.txt
+++ b/cmake/externals/glad45/CMakeLists.txt
@@ -5,7 +5,7 @@ include(SelectLibraryConfigurations)
 
 ExternalProject_Add(
   ${EXTERNAL_NAME}
-  URL https://public.highfidelity.com/dependencies/glad/glad45.zip
+  URL "${EXTERNAL_BUILD_ASSETS}/dependencies/glad/glad45.zip"
   URL_MD5 cfb19b3cb5b2f8f1d1669fb3150e5f05
   CONFIGURE_COMMAND CMAKE_ARGS -DCMAKE_BUILD_TYPE=${CMAKE_BUILD_TYPE} -DCMAKE_INSTALL_PREFIX:PATH=<INSTALL_DIR> -DCMAKE_POSITION_INDEPENDENT_CODE=ON
   LOG_DOWNLOAD 1
diff --git a/cmake/externals/hifiAudioCodec/CMakeLists.txt b/cmake/externals/hifiAudioCodec/CMakeLists.txt
index 5d439cd519..31454ace50 100644
--- a/cmake/externals/hifiAudioCodec/CMakeLists.txt
+++ b/cmake/externals/hifiAudioCodec/CMakeLists.txt
@@ -6,16 +6,16 @@ set(EXTERNAL_NAME hifiAudioCodec)
 string(TOUPPER ${EXTERNAL_NAME} EXTERNAL_NAME_UPPER)
 
 if (WIN32)
-  set(DOWNLOAD_URL https://public.highfidelity.com/dependencies/codecSDK-win-2.0.zip)
+  set(DOWNLOAD_URL "${EXTERNAL_BUILD_ASSETS}/dependencies/codecSDK-win-2.0.zip")
   set(DOWNLOAD_MD5 9199d4dbd6b16bed736b235efe980e67)
 elseif (APPLE)
-  set(DOWNLOAD_URL https://public.highfidelity.com/dependencies/codecSDK-mac-2.0.zip)
+  set(DOWNLOAD_URL "${EXTERNAL_BUILD_ASSETS}/dependencies/codecSDK-mac-2.0.zip")
   set(DOWNLOAD_MD5 21649881e7d5dc94f922179be96f76ba)
 elseif (ANDROID)
-  set(DOWNLOAD_URL https://public.highfidelity.com/dependencies/codecSDK-android-2.0.zip)
+  set(DOWNLOAD_URL "${EXTERNAL_BUILD_ASSETS}/dependencies/codecSDK-android-2.0.zip")
   set(DOWNLOAD_MD5 aef2a852600d498d58aa586668191683)
 elseif (UNIX)
-  set(DOWNLOAD_URL https://public.highfidelity.com/dependencies/codecSDK-linux-2.0.zip)
+  set(DOWNLOAD_URL "${EXTERNAL_BUILD_ASSETS}/dependencies/codecSDK-linux-2.0.zip")
   set(DOWNLOAD_MD5 67fb7755f9bcafb98a9fceea53bc7481)
 else()
   return()
diff --git a/cmake/externals/neuron/CMakeLists.txt b/cmake/externals/neuron/CMakeLists.txt
index 049e175354..45b18f86cd 100644
--- a/cmake/externals/neuron/CMakeLists.txt
+++ b/cmake/externals/neuron/CMakeLists.txt
@@ -4,7 +4,7 @@ set(EXTERNAL_NAME neuron)
 
 string(TOUPPER ${EXTERNAL_NAME} EXTERNAL_NAME_UPPER)
 
-set(NEURON_URL "https://public.highfidelity.com/dependencies/neuron_datareader_b.12.2.zip")
+set(NEURON_URL "${EXTERNAL_BUILD_ASSETS}/dependencies/neuron_datareader_b.12.2.zip")
 set(NEURON_URL_MD5 "84273ad2200bf86a9279d1f412a822ca")
 
 ExternalProject_Add(${EXTERNAL_NAME}
diff --git a/cmake/externals/polyvox/CMakeLists.txt b/cmake/externals/polyvox/CMakeLists.txt
index e5c3521b63..63a4bee043 100644
--- a/cmake/externals/polyvox/CMakeLists.txt
+++ b/cmake/externals/polyvox/CMakeLists.txt
@@ -7,7 +7,7 @@ set(CMAKE_BUILD_TYPE Release)
 
 ExternalProject_Add(
   ${EXTERNAL_NAME}
-  URL https://public.highfidelity.com/dependencies/polyvox-master-2015-7-15.zip
+  URL "${EXTERNAL_BUILD_ASSETS}/dependencies/polyvox-master-2015-7-15.zip"
   URL_MD5 9ec6323b87e849ae36e562ae1c7494a9
   CMAKE_ARGS -DENABLE_EXAMPLES=OFF -DENABLE_BINDINGS=OFF -DCMAKE_INSTALL_PREFIX:PATH=<INSTALL_DIR> -DCMAKE_BUILD_TYPE=${CMAKE_BUILD_TYPE}
   BINARY_DIR ${EXTERNAL_PROJECT_PREFIX}/build
diff --git a/cmake/externals/quazip/CMakeLists.txt b/cmake/externals/quazip/CMakeLists.txt
index f99d995a0c..8190a35988 100644
--- a/cmake/externals/quazip/CMakeLists.txt
+++ b/cmake/externals/quazip/CMakeLists.txt
@@ -18,7 +18,7 @@ endif ()
 
 ExternalProject_Add(
   ${EXTERNAL_NAME}
-  URL https://public.highfidelity.com/dependencies/quazip-0.7.3.zip
+  URL "${EXTERNAL_BUILD_ASSETS}/dependencies/quazip-0.7.3.zip"
   URL_MD5 ed03754d39b9da1775771819b8001d45
   BINARY_DIR ${EXTERNAL_PROJECT_PREFIX}/build
   CMAKE_ARGS ${QUAZIP_CMAKE_ARGS}
diff --git a/cmake/externals/sixense/CMakeLists.txt b/cmake/externals/sixense/CMakeLists.txt
index 35f7758820..c2fb8ad8f9 100644
--- a/cmake/externals/sixense/CMakeLists.txt
+++ b/cmake/externals/sixense/CMakeLists.txt
@@ -4,15 +4,15 @@ set(EXTERNAL_NAME sixense)
 
 string(TOUPPER ${EXTERNAL_NAME} EXTERNAL_NAME_UPPER)
 
-#set(SIXENSE_URL "https://public.highfidelity.com/dependencies/SixenseSDK_062612.zip")
+#set(SIXENSE_URL "${EXTERNAL_BUILD_ASSETS}/dependencies/SixenseSDK_062612.zip")
 #set(SIXENSE_URL_MD5 "10cc8dc470d2ac1244a88cf04bc549cc")
 #set(SIXENSE_NEW_LAYOUT 0)
 
-set(SIXENSE_URL "https://public.highfidelity.com/dependencies/SixenseSDK_071615.zip")
+set(SIXENSE_URL "${EXTERNAL_BUILD_ASSETS}/dependencies/SixenseSDK_071615.zip")
 set(SIXENSE_URL_MD5 "752a3901f334124e9cffc2ba4136ef7d")
 set(SIXENSE_NEW_LAYOUT 1)
 
-#set(SIXENSE_URL "https://public.highfidelity.com/dependencies/SixenseSDK_102215.zip")
+#set(SIXENSE_URL "${EXTERNAL_BUILD_ASSETS}/dependencies/SixenseSDK_102215.zip")
 #set(SIXENSE_URL_MD5 "93c3a6795cce777a0f472b09532935f1")
 #set(SIXENSE_NEW_LAYOUT 1)
 
diff --git a/cmake/externals/steamworks/CMakeLists.txt b/cmake/externals/steamworks/CMakeLists.txt
index eb61d22f8b..1ec72d7d28 100644
--- a/cmake/externals/steamworks/CMakeLists.txt
+++ b/cmake/externals/steamworks/CMakeLists.txt
@@ -4,7 +4,7 @@ set(EXTERNAL_NAME steamworks)
 
 string(TOUPPER ${EXTERNAL_NAME} EXTERNAL_NAME_UPPER)
 
-set(STEAMWORKS_URL "https://public.highfidelity.com/dependencies/steamworks_sdk_137.zip")
+set(STEAMWORKS_URL "${EXTERNAL_BUILD_ASSETS}/dependencies/steamworks_sdk_137.zip")
 set(STEAMWORKS_URL_MD5 "95ba9d0e3ddc04f8a8be17d2da806cbb")
 
 ExternalProject_Add(
diff --git a/cmake/externals/tbb/CMakeLists.txt b/cmake/externals/tbb/CMakeLists.txt
index 1788922ef2..8f8f2d3030 100644
--- a/cmake/externals/tbb/CMakeLists.txt
+++ b/cmake/externals/tbb/CMakeLists.txt
@@ -3,13 +3,13 @@ set(EXTERNAL_NAME tbb)
 include(ExternalProject)
 
 if (WIN32)
-  set(DOWNLOAD_URL https://public.highfidelity.com/dependencies/tbb2017_20170604oss_win_slim.zip)
+  set(DOWNLOAD_URL "${EXTERNAL_BUILD_ASSETS}/dependencies/tbb2017_20170604oss_win_slim.zip")
   set(DOWNLOAD_MD5 065934458e3db88397f3d10e7eea536c)
 elseif (APPLE)
-  set(DOWNLOAD_URL https://public.highfidelity.com/dependencies/tbb2017_20170604oss_mac_slim.tar.gz)
+  set(DOWNLOAD_URL "${EXTERNAL_BUILD_ASSETS}/dependencies/tbb2017_20170604oss_mac_slim.tar.gz")
   set(DOWNLOAD_MD5 62bde626b396f8e1a85c6a8ded1d8105)
 else ()
-  set(DOWNLOAD_URL https://public.highfidelity.com/dependencies/tbb2017_20170604oss_lin_slim.tar.gz)
+  set(DOWNLOAD_URL "${EXTERNAL_BUILD_ASSETS}/dependencies/tbb2017_20170604oss_lin_slim.tar.gz")
   set(DOWNLOAD_MD5 2a5c721f40fa3503ffc12c18dd00011c)
 endif ()
 
diff --git a/cmake/externals/vhacd/CMakeLists.txt b/cmake/externals/vhacd/CMakeLists.txt
index fe19f7ac7a..5fb89b7e9b 100644
--- a/cmake/externals/vhacd/CMakeLists.txt
+++ b/cmake/externals/vhacd/CMakeLists.txt
@@ -7,7 +7,7 @@ endif ()
 include(ExternalProject)
 ExternalProject_Add(
   ${EXTERNAL_NAME}
-  URL https://public.highfidelity.com/dependencies/v-hacd-master.zip
+  URL "${EXTERNAL_BUILD_ASSETS}/dependencies/v-hacd-master.zip"
   URL_MD5 3bfc94f8dd3dfbfe8f4dc088f4820b3e
   CMAKE_ARGS ${ANDROID_CMAKE_ARGS} -DCMAKE_INSTALL_PREFIX:PATH=<INSTALL_DIR>
   BINARY_DIR ${EXTERNAL_PROJECT_PREFIX}/build
diff --git a/cmake/externals/wasapi/CMakeLists.txt b/cmake/externals/wasapi/CMakeLists.txt
index 286d18e2b5..bc8148c278 100644
--- a/cmake/externals/wasapi/CMakeLists.txt
+++ b/cmake/externals/wasapi/CMakeLists.txt
@@ -6,7 +6,7 @@ if (WIN32)
   include(ExternalProject)
   ExternalProject_Add(
     ${EXTERNAL_NAME}
-    URL https://public.highfidelity.com/dependencies/qtaudio_wasapi13.zip
+    URL "${EXTERNAL_BUILD_ASSETS}/dependencies/qtaudio_wasapi13.zip"
     URL_MD5 aa56a45f19c18caee13d29a40d1d7d28
     CONFIGURE_COMMAND ""
     BUILD_COMMAND ""
diff --git a/cmake/ports/openssl-android/portfile.cmake b/cmake/ports/openssl-android/portfile.cmake
index 54936d254d..372a9fceef 100644
--- a/cmake/ports/openssl-android/portfile.cmake
+++ b/cmake/ports/openssl-android/portfile.cmake
@@ -2,10 +2,12 @@ include(vcpkg_common_functions)
 set(OPENSSL_VERSION 1.1.0g)
 set(MASTER_COPY_SOURCE_PATH ${CURRENT_BUILDTREES_DIR}/src)
 
+file(READ "${VCPKG_ROOT_DIR}/_env/EXTERNAL_BUILD_ASSETS.txt" EXTERNAL_BUILD_ASSETS)
+
 message("MASTER_COPY_SOURCE_PATH ${MASTER_COPY_SOURCE_PATH}")
 vcpkg_download_distfile(
     OPENSSL_SOURCE_ARCHIVE
-    URLS https://hifi-public.s3.amazonaws.com/dependencies/android/openssl-1.1.0g_armv8.tgz?versionId=AiiPjmgUZTgNj7YV1EEx2lL47aDvvvAW
+    URLS "${EXTERNAL_BUILD_ASSETS}/dependencies/android/openssl-1.1.0g_armv8.tgz?versionId=AiiPjmgUZTgNj7YV1EEx2lL47aDvvvAW"
     SHA512 5d7bb6e5d3db2340449e2789bcd72da821f0e57483bac46cf06f735dffb5d73c1ca7cc53dd48f3b3979d0fe22b3ae61997c516fc0c4611af4b4b7f480e42b992
     FILENAME openssl-1.1.0g_armv8.tgz
 )
diff --git a/cmake/ports/webrtc/portfile.cmake b/cmake/ports/webrtc/portfile.cmake
index b5b46723bd..fdc653d6a5 100644
--- a/cmake/ports/webrtc/portfile.cmake
+++ b/cmake/ports/webrtc/portfile.cmake
@@ -2,19 +2,21 @@ include(vcpkg_common_functions)
 set(WEBRTC_VERSION 20190626)
 set(MASTER_COPY_SOURCE_PATH ${CURRENT_BUILDTREES_DIR}/src)
 
+file(READ "${VCPKG_ROOT_DIR}/_env/EXTERNAL_BUILD_ASSETS.txt" EXTERNAL_BUILD_ASSETS)
+
 if (ANDROID)
    # this is handled by hifi_android.py
 elseif (WIN32)
     vcpkg_download_distfile(
         WEBRTC_SOURCE_ARCHIVE
-        URLS https://hifi-public.s3.amazonaws.com/seth/webrtc-20190626-windows.zip
+        URLS "${EXTERNAL_BUILD_ASSETS}/seth/webrtc-20190626-windows.zip"
         SHA512 c0848eddb1579b3bb0496b8785e24f30470f3c477145035fd729264a326a467b9467ae9f426aa5d72d168ad9e9bf2c279150744832736bdf39064d24b04de1a3
         FILENAME webrtc-20190626-windows.zip
     )
 elseif (APPLE)
     vcpkg_download_distfile(
         WEBRTC_SOURCE_ARCHIVE
-        URLS https://hifi-public.s3.amazonaws.com/seth/webrtc-m78-osx.tar.gz
+        URLS "${EXTERNAL_BUILD_ASSETS}/seth/webrtc-m78-osx.tar.gz"
         SHA512 8b547da921cc96f5c22b4253a1c9e707971bb627898fbdb6b238ef1318c7d2512e878344885c936d4bd6a66005cc5b63dfc3fa5ddd14f17f378dcaa17b5e25df
         FILENAME webrtc-m78-osx.tar.gz
     )
@@ -22,7 +24,7 @@ else ()
     # else Linux desktop
     vcpkg_download_distfile(
         WEBRTC_SOURCE_ARCHIVE
-        URLS https://hifi-public.s3.amazonaws.com/seth/webrtc-20190626-linux.tar.gz
+        URLS "${EXTERNAL_BUILD_ASSETS}/seth/webrtc-20190626-linux.tar.gz"
         SHA512 07d7776551aa78cb09a3ef088a8dee7762735c168c243053b262083d90a1d258cec66dc386f6903da5c4461921a3c2db157a1ee106a2b47e7756cb424b66cc43
         FILENAME webrtc-20190626-linux.tar.gz
     )
diff --git a/hifi_vcpkg.py b/hifi_vcpkg.py
index 6ec2184d45..94cac9afa2 100644
--- a/hifi_vcpkg.py
+++ b/hifi_vcpkg.py
@@ -9,6 +9,7 @@ import tempfile
 import json
 import xml.etree.ElementTree as ET
 import functools
+from os import path
 
 print = functools.partial(print, flush=True)
 
@@ -36,6 +37,7 @@ endif()
         self.sourcePortsPath = args.ports_path
         self.id = hifi_utils.hashFolder(self.sourcePortsPath)[:8]
         self.configFilePath = os.path.join(args.build_root, 'vcpkg.cmake')
+        self.assets_url = self.readVar('EXTERNAL_BUILD_ASSETS')
 
         # OS dependent information
         system = platform.system()
@@ -72,19 +74,19 @@ endif()
         if 'Windows' == system:
             self.exe = os.path.join(self.path, 'vcpkg.exe')
             self.bootstrapCmd = 'bootstrap-vcpkg.bat'
-            self.vcpkgUrl = 'https://hifi-public.s3.amazonaws.com/dependencies/vcpkg/vcpkg-win32.tar.gz?versionId=YZYkDejDRk7L_hrK_WVFthWvisAhbDzZ'
+            self.vcpkgUrl = self.assets_url + '/dependencies/vcpkg/vcpkg-win32.tar.gz%3FversionId=YZYkDejDRk7L_hrK_WVFthWvisAhbDzZ'
             self.vcpkgHash = '3e0ff829a74956491d57666109b3e6b5ce4ed0735c24093884317102387b2cb1b2cd1ff38af9ed9173501f6e32ffa05cc6fe6d470b77a71ca1ffc3e0aa46ab9e'
             self.hostTriplet = 'x64-windows'
         elif 'Darwin' == system:
             self.exe = os.path.join(self.path, 'vcpkg')
             self.bootstrapCmd = 'bootstrap-vcpkg.sh'
-            self.vcpkgUrl = 'https://hifi-public.s3.amazonaws.com/dependencies/vcpkg/vcpkg-osx.tar.gz?versionId=_fhqSxjfrtDJBvEsQ8L_ODcdUjlpX9cc'
+            self.vcpkgUrl = self.assets_url + '/dependencies/vcpkg/vcpkg-osx.tar.gz%3FversionId=_fhqSxjfrtDJBvEsQ8L_ODcdUjlpX9cc'
             self.vcpkgHash = '519d666d02ef22b87c793f016ca412e70f92e1d55953c8f9bd4ee40f6d9f78c1df01a6ee293907718f3bbf24075cc35492fb216326dfc50712a95858e9cbcb4d'
             self.hostTriplet = 'x64-osx'
         else:
             self.exe = os.path.join(self.path, 'vcpkg')
             self.bootstrapCmd = 'bootstrap-vcpkg.sh'
-            self.vcpkgUrl = 'https://hifi-public.s3.amazonaws.com/dependencies/vcpkg/vcpkg-linux.tar.gz?versionId=97Nazh24etEVKWz33XwgLY0bvxEfZgMU'
+            self.vcpkgUrl = self.assets_url + '/dependencies/vcpkg/vcpkg-linux.tar.gz%3FversionId=97Nazh24etEVKWz33XwgLY0bvxEfZgMU'
             self.vcpkgHash = '6a1ce47ef6621e699a4627e8821ad32528c82fce62a6939d35b205da2d299aaa405b5f392df4a9e5343dd6a296516e341105fbb2dd8b48864781d129d7fba10d'
             self.hostTriplet = 'x64-linux'
 
@@ -94,6 +96,10 @@ endif()
         else:
             self.triplet = self.hostTriplet
 
+    def readVar(self, var):
+        with open(os.path.join(self.args.build_root, '_env', var + ".txt")) as fp:
+            return fp.read()
+
     def upToDate(self):
         # Prevent doing a clean if we've explcitly set a directory for vcpkg
         if self.args.vcpkg_root is not None:
@@ -115,6 +121,17 @@ endif()
             return False
         return True
 
+    def copyEnv(self):
+        print("Passing on variables to vcpkg")
+        srcEnv = os.path.join(self.args.build_root, "_env")
+        destEnv = os.path.join(self.path, "_env")
+
+        if path.exists(destEnv):
+            shutil.rmtree(destEnv)
+
+        shutil.copytree(srcEnv, destEnv)
+
+
     def clean(self):
         print("Cleaning vcpkg installation at {}".format(self.path))
         if os.path.isdir(self.path):
@@ -124,6 +141,7 @@ endif()
     # Make sure the VCPKG prerequisites are all there.
     def bootstrap(self):
         if self.upToDate():
+            self.copyEnv()
             return
 
         self.clean()
@@ -160,6 +178,7 @@ endif()
         if (os.path.isdir(portsPath)):
             shutil.rmtree(portsPath, ignore_errors=True)
         shutil.copytree(self.sourcePortsPath, portsPath)
+        self.copyEnv()
 
     def run(self, commands):
         actualCommands = [self.exe, '--vcpkg-root', self.path]
@@ -199,7 +218,7 @@ endif()
         # vcpkg prebuilt
         if not os.path.isdir(os.path.join(self.path, 'installed', 'arm64-android')):
             dest = os.path.join(self.path, 'installed')
-            url = "https://hifi-public.s3.amazonaws.com/dependencies/vcpkg/vcpkg-arm64-android.tar.gz"
+            url = self.assets_url + "/dependencies/vcpkg/vcpkg-arm64-android.tar.gz"
             # FIXME I don't know why the hash check frequently fails here.  If you examine the file later it has the right hash
             #hash = "832f82a4d090046bdec25d313e20f56ead45b54dd06eee3798c5c8cbdd64cce4067692b1c3f26a89afe6ff9917c10e4b601c118bea06d23f8adbfe5c0ec12bc3"
             #hifi_utils.downloadAndExtract(url, dest, hash)
@@ -263,14 +282,14 @@ endif()
 
             url = 'NOT DEFINED'
             if platform.system() == 'Windows':
-                url = 'https://hifi-public.s3.amazonaws.com/dependencies/vcpkg/qt5-install-5.12.3-windows3.tar.gz'
+                url = self.assets_url + '/dependencies/vcpkg/qt5-install-5.12.3-windows3.tar.gz'
             elif platform.system() == 'Darwin':
-                url = 'https://hifi-public.s3.amazonaws.com/dependencies/vcpkg/qt5-install-5.12.3-macos.tar.gz?versionId=bLAgnoJ8IMKpqv8NFDcAu8hsyQy3Rwwz'
+                url = self.assets_url + '/dependencies/vcpkg/qt5-install-5.12.3-macos.tar.gz%3FversionId=bLAgnoJ8IMKpqv8NFDcAu8hsyQy3Rwwz'
             elif platform.system() == 'Linux':
                 if platform.linux_distribution()[1][:3] == '16.':
-                    url = 'https://hifi-public.s3.amazonaws.com/dependencies/vcpkg/qt5-install-5.12.3-ubuntu-16.04-with-symbols.tar.gz'
+                    url = self.assets_url + '/dependencies/vcpkg/qt5-install-5.12.3-ubuntu-16.04-with-symbols.tar.gz'
                 elif platform.linux_distribution()[1][:3] == '18.':
-                    url = 'https://hifi-public.s3.amazonaws.com/dependencies/vcpkg/qt5-install-5.12.3-ubuntu-18.04.tar.gz'
+                    url = self.assets_url + '/dependencies/vcpkg/qt5-install-5.12.3-ubuntu-18.04.tar.gz'
                 else:
                     print('UNKNOWN LINUX VERSION!!!')
                     return;
diff --git a/launchers/qt/CMakeLists.txt b/launchers/qt/CMakeLists.txt
index 8155400f45..596f3b7d5c 100644
--- a/launchers/qt/CMakeLists.txt
+++ b/launchers/qt/CMakeLists.txt
@@ -45,7 +45,7 @@ if (WIN32)
 
     ExternalProject_Add(
         qtlite
-        URL "https://public.highfidelity.com/dependencies/qtlite/qt-lite-5.9.9-win-oct-15-2019.zip"
+        URL "${EXTERNAL_BUILD_ASSETS}/dependencies/qtlite/qt-lite-5.9.9-win-oct-15-2019.zip"
         URL_HASH MD5=0176277bca37d219e83738caf3a698eb
         CONFIGURE_COMMAND ""
         BUILD_COMMAND ""
@@ -78,7 +78,7 @@ endif ()
 if (APPLE)
   ExternalProject_Add(
     qtlite
-    URL "https://public.highfidelity.com/dependencies/qtlite/qt-lite-5.9.9-mac.zip"
+    URL "${EXTERNAL_BUILD_ASSETS}/dependencies/qtlite/qt-lite-5.9.9-mac.zip"
     URL_HASH MD5=0cd78d40e5f539a7e314cf99b6cae0d0
     CONFIGURE_COMMAND ""
     BUILD_COMMAND ""