[clang] [clang][driver] Suppress gnu-line-marker when saving temps (PR #134621)

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macurtis-amd wrote:

> I don't, but I wonder what's the GCC behavior. It seems to suppress the diagnostic when processing a .i file.

Diagnostic seems to be suppressed by [-fpreprocessed](https://gcc.gnu.org/onlinedocs/gcc/Preprocessor-Options.html#index-fpreprocessed), which is implicit if you pass a `.i` file to `gcc` and passed explicitly to `cc1` when using `-save-temps`.

I guess the analogous clang option is `-x`?

https://github.com/llvm/llvm-project/pull/134621