[libc] Remove direct math.h includes (#85324)

Reland of #84991

A downstream overlay mode user ran into issues with the isnan macro not
working in our sources with a specific libc configuration. This patch
replaces the last direct includes of math.h with our internal
math_macros.h, along with the necessary build system changes.

libc/fuzzing/CMakeLists.txt

@@ -1,7 +1,8 @@
 set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fsanitize=fuzzer")
 add_custom_target(libc-fuzzer)
 
-add_subdirectory(math)
+# TODO(#85680): Re-enable math fuzzing after headers are sorted out
+# add_subdirectory(math)
 add_subdirectory(stdlib)
 add_subdirectory(stdio)
 add_subdirectory(string)

libc/fuzzing/math/RemQuoDiff.h

@@ -11,7 +11,7 @@
 
 #include "src/__support/FPUtil/FPBits.h"
 
-#include <math.h>
+#include "include/llvm-libc-macros/math-macros.h"
 #include <stddef.h>
 #include <stdint.h>
 

libc/fuzzing/math/SingleInputSingleOutputDiff.h

@@ -10,9 +10,7 @@
 #define LLVM_LIBC_FUZZING_MATH_SINGLE_INPUT_SINGLE_OUTPUT_DIFF_H
 
 #include "fuzzing/math/Compare.h"
-#include "src/__support/FPUtil/FPBits.h"
 
-#include <math.h>
 #include <stddef.h>
 #include <stdint.h>
 

libc/fuzzing/math/TwoInputSingleOutputDiff.h

@@ -10,9 +10,7 @@
 #define LLVM_LIBC_FUZZING_MATH_TWO_INPUT_SINGLE_OUTPUT_DIFF_H
 
 #include "fuzzing/math/Compare.h"
-#include "src/__support/FPUtil/FPBits.h"
 
-#include <math.h>
 #include <stddef.h>
 #include <stdint.h>
 

libc/fuzzing/stdlib/strtofloat_fuzz.cpp

@@ -16,7 +16,7 @@
 
 #include "src/__support/FPUtil/FPBits.h"
 
-#include <math.h>
+#include "include/llvm-libc-macros/math-macros.h"
 #include <stddef.h>
 #include <stdint.h>