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

[via llvm-commits]

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@@ -3,7 +3,7 @@ add_header_library(
   HDRS
     FEnvImpl.h
   DEPENDS
-    libc.include.fenv
+    libc.include.fenv 
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lntue wrote:

also add `libc.hdr.fenv_macros` dependency here.

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