[libc] Also remove _FORTIFY_SOURCE before including <stdlib.h> in overlay mode. (#142647)

Author: lntue

libc/hdr/stdlib_overlay.h

@@ -19,6 +19,11 @@
 // functions, causing external alias errors.  They are guarded by
 // `__USE_FORTIFY_LEVEL`, which will be temporarily disabled.
 
+#ifdef _FORTIFY_SOURCE
+#define LIBC_OLD_FORTIFY_SOURCE _FORTIFY_SOURCE
+#undef _FORTIFY_SOURCE
+#endif
+
 #ifdef __USE_FORTIFY_LEVEL
 #define LIBC_OLD_USE_FORTIFY_LEVEL __USE_FORTIFY_LEVEL
 #undef __USE_FORTIFY_LEVEL
@@ -27,6 +32,11 @@
 
 #include <stdlib.h>
 
+#ifdef LIBC_OLD_FORTIFY_SOURCE
+#define _FORTIFY_SOURCE LIBC_OLD_FORTIFY_SOURCE
+#undef LIBC_OLD_FORTIFY_SOURCE
+#endif
+
 #ifdef LIBC_OLD_USE_FORTIFY_LEVEL
 #undef __USE_FORTIFY_LEVEL
 #define __USE_FORTIFY_LEVEL LIBC_OLD_USE_FORTIFY_LEVEL