[clang] [AIX] Turn on `#pragma mc_func` check by default (PR #101336)

[Qiongsi Wu via cfe-commits]

================
@@ -562,7 +562,7 @@ void AIX::addClangTargetOptions(
     CC1Args.push_back("-fno-sized-deallocation");
 
   if (Args.hasFlag(options::OPT_ferr_pragma_mc_func_aix,
-                   options::OPT_fno_err_pragma_mc_func_aix, false))
+                   options::OPT_fno_err_pragma_mc_func_aix, true))
----------------
qiongsiwu wrote:

Good point! Code is revised. 

I tried the suggested change
```
if (Args.hasArg(options::OPT_fno_err_pragma_mc_func_aix))
   CC1Args.push_back("-fno-err-pragma-mc-func-aix");
```
But it does not handle situations like `-fno-err-pragma-mc-func-aix -ferr-pragma-mc-func-aix` correctly. I think we still need to process both flags in the driver, but we only need to pass `-fno-err-pragma-mc-func-aix` to CC1. Did I miss something? 

https://github.com/llvm/llvm-project/pull/101336