[clang] [clang] Support -Wa, options -mmsa and -mno-msa (PR #99615)

[Fangrui Song via cfe-commits]

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@@ -2507,6 +2507,7 @@ static void CollectArgsForIntegratedAssembler(Compilation &C,
   bool Crel = false, ExperimentalCrel = false;
   bool UseRelaxRelocations = C.getDefaultToolChain().useRelaxRelocations();
   bool UseNoExecStack = false;
+  bool Msa = false;
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MaskRay wrote:

Please do use `std::optional<bool> Msa` and please don't add `err_drv_msa_and_nomsa`. It's common for `-Wa,--foo` to override a previous `-Wa,--no-foo`. There shouldn't be an error.

https://github.com/llvm/llvm-project/pull/99615