Fix to addd EMSCRIPTEN_SYSROOT into internal SYSROOT variable.

[ci skip]

CMakeLists.txt

@@ -72,7 +72,7 @@ set (DEST_BUNDLE_DIR ${DEST_SHARE_DIR}/Applications)
 # Note to package maintainer: ${PATH_SUFFIX} for library could be removed if the extra path is not desired, but if so then the RPATH setting in Source's CMakeLists.txt needs to be adjusted accordingly
 set (DEST_LIBRARY_DIR lib${LIB_SUFFIX}/${PATH_SUFFIX})
 # TODO: Investigate the implication of using CMAKE_SYSROOT variable (available since 3.0.0) instead of our own SYSROOT variable
-set (SYSROOT ${ANDROID_TOOLCHAIN_ROOT} ${RPI_SYSROOT} ${MINGW_SYSROOT} ${IOS_SYSROOT} CACHE INTERNAL "Path to system root of the cross-compiling target")  # SYSROOT is empty for native build
+set (SYSROOT ${ANDROID_TOOLCHAIN_ROOT} ${RPI_SYSROOT} ${MINGW_SYSROOT} ${IOS_SYSROOT} ${EMSCRIPTEN_SYSROOT} CACHE INTERNAL "Path to system root of the cross-compiling target")  # SYSROOT is empty for native build
 set (DEST_PKGCONFIG_DIR lib${LIB_SUFFIX}/pkgconfig)
 # Install application launcher scripts
 file (GLOB APP_SCRIPTS ${CMAKE_SOURCE_DIR}/bin/*${SCRIPT_EXT})