[libc] Include FP_* macros in math.h (llvm#84996)

These are used unconditionally by libc++ math.h.

This is related to issue llvm#84879.

Author: petrhosek

libc/include/llvm-libc-macros/math-macros.h

@@ -11,6 +11,12 @@
 
 #include "limits-macros.h"
 
+#define FP_NAN 0
+#define FP_INFINITE 1
+#define FP_ZERO 2
+#define FP_SUBNORMAL 3
+#define FP_NORMAL 4
+
 #define MATH_ERRNO 1
 #define MATH_ERREXCEPT 2