[clang] [clang][CodeGen] Ensure consistent `mustprogress` attribute emission across all paths (PR #71452)

[Antonio Frighetto via cfe-commits]

antoniofrighetto wrote:

I wonder if we should have `return getLangOpts().CPlusPlus11 || getLangOpts().C11;` at line 586:

https://github.com/llvm/llvm-project/blob/d1fb9307951319eea3e869d78470341d603c8363/clang/lib/CodeGen/CodeGenFunction.h#L573-L587

But I couldn't find anything strictly related in C11 7.26 and 7.31.15.

https://github.com/llvm/llvm-project/pull/71452