C++ feature checks: Filter out warnings caused by user flags
Filter out -Winvalid-command-line-argument
warnings from Clang (that can be caused by user-specified flags) so that they do not break our checks for C++ feature availability.
Filter out -Winvalid-command-line-argument
warnings from Clang (that can be caused by user-specified flags) so that they do not break our checks for C++ feature availability.