[libc] [llvm] [libc] Add proxy header for fenv.h macro constants. #87863 (PR #87896)

[via llvm-commits]

================
@@ -6,17 +6,17 @@
  * SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
  */
 
+#include "mathlib.h"
----------------
lntue wrote:

Revert the changes in this file.

https://github.com/llvm/llvm-project/pull/87896