[CMake] Ensure `CLANG_RESOURCE_DIR` is respected.

re-commit of 39aa0f5c434b463520ac39a8dbe933ee8c4c5ea7 with missing file:
cmake/Modules/GetClangResourceDir.cmake.

GitOrigin-RevId: 0beffb854209a41f31beb18f9631258349a99299
1 file changed