This uses a variable that can be overriden with an environment variable.
This makes it easy for the community to create alternate asset hosts.
Due to vcpkg using a clean environment, variables can't be easily passed
to cmake scripts run by vcpkg. This was worked around by writing the data
that needs to be passed into temporary files and reading it from the
vcpkg ports.
23> CMake Warning (dev) at C:/msys64/home/Anthony/code/hifi/build/ext/vc12/quazip/project/src/quazip-stamp/quazip-configure-Debug.cmake:3 (set):
23> Syntax error in cmake code at
23>
23> C:/msys64/home/Anthony/code/hifi/build/ext/vc12/quazip/project/src/quazip-stamp/quazip-configure-Debug.cmake:3
23>
23> when parsing string
23>
23> C:/Program Files (x86)/CMake/bin/cmake.exe;-DCMAKE_INSTALL_PREFIX:PATH=C:/msys64/home/Anthony/code/hifi/build/ext/vc12/quazip/project;-DCMAKE_PREFIX_PATH=C:\Qt\Qt5.5.1\5.5\msvc2013\lib\cmake;-DCMAKE_INSTALL_NAME_DIR:PATH=C:/msys64/home/Anthony/code/hifi/build/ext/vc12/quazip/project/lib;-DZLIB_ROOT=C:/msys64/home/Anthony/code/hifi/build/ext/vc12/zlib/project;-GVisual Studio 12 2013;C:/msys64/home/Anthony/code/hifi/build/ext/vc12/quazip/project/src/quazip
23>
23> Invalid escape sequence \Q
23>
23> Policy CMP0010 is not set: Bad variable reference syntax is an error. Run
23> "cmake --help-policy CMP0010" for policy details. Use the cmake_policy
23> command to set the policy and suppress this warning.
23> This warning is for project developers. Use -Wno-dev to suppress it.
By converting backslashes to slashes before using the QT_CMAKE_PREFIX_PATH environment variable on the command line.
