Fix -Wno-error= parsing in clang-format.

As noted in parsing of
the clang-format parameter -Wno-error=unknown fails.
This currently is done by having `-Wno-error=unknown` as an option.
In this patch this is changed to make `-Wno-error=` parse an enum into a bit set.
This way the parsing is fixed and also we can possibly add new options easily.

Reviewed By: MyDeveloperDay

Differential Revision:

GitOrigin-RevId: c755e41c336c898873db6c3c58a2819a982f60de
1 file changed