[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 agree that `-include-pch` is ClangOption and CC1Option and is visible to compiler (`clang`) and compiler frontend (`clang -cc1`). However, `-emit-pch` (NOT `-include-pch`) is CC1Option and is only visible to compiler frontend (clang -cc1) as mentioned in my previous reply. 

For example:

If I compile the code using the following command line to check Driver support:
```
$ clang test.h -emit-pch -o test.h.pch
```
I got the following error:
```
clang: error: unknown argument '-emit-pch'; did you mean '-Xclang -emit-pch'?
```
In addition, I found a old PR *https://reviews.llvm.org/D87325) which try to add -emit-pch option to clang driver, but not pass the code review.

I am wondering  why `-emit-pch` is CC1 only option but `-include-pch` is both ClangOption and CC1Option?


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