[clang] [Frontend][PCH]-Add support for ignoring PCH options (-ignore-pch). (PR #142409)

[Matheus Izvekov via cfe-commits]

https://github.com/mizvekov approved this pull request.

Thanks, LGTM on the implementation.

I have no objections to the flag itself either.

This is missing a Release note, please add it before merging.

CC @ChuanqiXu9 

Please wait at least a couple of days before merging for other comments and opinions.

https://github.com/llvm/llvm-project/pull/142409