cmake HAVE_FILESYSTEM_IN_STD examples

scp-fs2open/fs2open.github.com lib/openxr/src/cmake/StdFilesystemFlags.cmake :113 

check_cxx_source_compiles("${_stdfs_source}" HAVE_FILESYSTEM_IN_STD)

RavEngine/RavEngine deps/OpenXR-SDK/src/cmake/StdFilesystemFlags.cmake :113 

check_cxx_source_compiles("${_stdfs_source}" HAVE_FILESYSTEM_IN_STD)

rbfx/rbfx Source/ThirdParty/OpenXRSDK/src/cmake/StdFilesystemFlags.cmake :113 

check_cxx_source_compiles("${_stdfs_source}" HAVE_FILESYSTEM_IN_STD)