add the app icon to gvr-interface

cmake/android/QtCreateAPK.cmake

@@ -36,6 +36,13 @@ macro(qt_create_apk)
   
 	# Create "AndroidManifest.xml"
 	configure_file("${ANDROID_THIS_DIRECTORY}/AndroidManifest.xml.in" "${ANDROID_APK_BUILD_DIR}/AndroidManifest.xml")
+  
+  # copy the res folder from the target to the apk build dir
+  add_custom_command(
+    TARGET ${TARGET_NAME}
+    POST_BUILD
+    COMMAND ${CMAKE_COMMAND} -E copy_directory "${CMAKE_CURRENT_SOURCE_DIR}/res" "${ANDROID_APK_BUILD_DIR}/res"
+  )
 
   # figure out where the qt dir is
   get_filename_component(QT_DIR "${QT_CMAKE_PREFIX_PATH}/../../" ABSOLUTE)