[libc] [llvm] [libc] Add proxy headers for fenv types. (PR #88467)

[Job Henandez Lara via llvm-commits]

Jobhdez wrote:

> looks great! nice job, thank you!
> 
> need us to merge? if so will do so next week (prefer not to merge Friday afternoon when it's time for 🍻

Sounds good! Enjoy your 🍻 

https://github.com/llvm/llvm-project/pull/88467