[clang] [Clang][OpenMP] Fix stdio.h wrapper when glibc includes again (PR #77017)

[Joel E. Denny via cfe-commits]

jdenny-ornl wrote:

> TYVM for fixing this. There's a lot of hacky stuff we need to do here to make it work, but it is what it is.
> 
> Guessing the other wrapped files are fine? I remember having problems with `cytype` and `string` but I hopefully resolved a lot of those already.

I do have remaining test failures I haven't yet sorted out on some of our systems, but I don't yet have reason to suspect they're related to these libc wrappers.

Thanks for the quick review.  Will push tomorrow when I have time to watch bots.

https://github.com/llvm/llvm-project/pull/77017