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

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MaggieYingYi wrote:

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

Added in the commit https://github.com/MaggieYingYi/llvm-project/commit/8a7df93f999633b7e237714a83811f2000d8351e. @mizvekov, could you please help me review the release note? Thanks

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