[clang] [clang][X86] Add __cpuidex function to cpuid.h (PR #97785)

[Aiden Grossman via cfe-commits]

boomanaiden154 wrote:

> Thanks - I think this is fine with me. In https://github.com/mingw-w64/mingw-w64/commit/a4c0c1d00d140d69a2c72f6ca0d49c91bdb2b08c we adjusted the mingw-w64 headers in anticipation that this gets merged in Clang 19, so it'd be good to have it settled before the 19.x branch gets made.

Sounds good. Assuming there aren't any objections, I'll try and land this on Wednesday given it's just a reland, has been approved in the past, and the remaining (identified) issues have been signed off on phabricator. That should give time in case anyone has comments but still give a reasonable enough time frame to ensure it sticks for clang 19.

https://github.com/llvm/llvm-project/pull/97785