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

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@@ -31,6 +31,16 @@ option:
 
   $ clang -cc1 -include-pch test.h.pch test.c -o test.s
 
+To ignore PCH options using ``clang -cc1``, use the option `-ignore-pch`:
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MaggieYingYi wrote:

I added `-ignore-pch` option followed the same way as `-emit-pch`. `-emit-pch` is CC1Option and is only visible to compiler frontend (`clang -cc1`). Since `-emit-pch` is only visible to compiler frontend, I added `-ignore-pch` option as CC1Option.

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