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

[Fangrui Song via cfe-commits]

================
@@ -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;
----------------
MaskRay wrote:

```
std::optional<bool> Msa

if (-mmsa) Msa = true;
if (-mno-msa) Msa = false;


if (Msa) {
  if (not mips) ...
  else if (*Msa) CmdArgs.push_back("-mmsa");
}
```

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