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

[Nick Desaulniers via llvm-commits]

================
@@ -119,6 +119,15 @@ libc_support_library(
 )
 
 libc_support_library(
+    name = "hdr_fenv_t",
----------------
nickdesaulniers wrote:

See  L140 `############################ Type Proxy Header Files ###########################`

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