[libc] Create a separate proxy header for math-function-macros.h (#98430)
Fix #98393
diff --git a/libc/hdr/math_function_macros.h b/libc/hdr/math_function_macros.h
new file mode 100644
index 0000000..48dec82
--- /dev/null
+++ b/libc/hdr/math_function_macros.h
@@ -0,0 +1,27 @@
+//===-- Definition of macros from math.h ----------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_HDR_MATH_FUNCTION_MACROS_H
+#define LLVM_LIBC_HDR_MATH_FUNCTION_MACROS_H
+
+#ifdef LIBC_FULL_BUILD
+
+#include "include/llvm-libc-macros/math-function-macros.h"
+
+#else // Overlay mode
+
+// GCC will include CXX headers when __cplusplus is defined. This behavior
+// can be suppressed by defining _GLIBCXX_INCLUDE_NEXT_C_HEADERS.
+#if defined(__GNUC__) && !defined(__clang__)
+#define _GLIBCXX_INCLUDE_NEXT_C_HEADERS
+#endif
+#include <math.h>
+
+#endif // LLVM_LIBC_FULL_BUILD
+
+#endif // LLVM_LIBC_HDR_MATH_MACROS_H
