Clean up more recursive FORTIFY_SOURCE calls

Don't use FORTIFY_SOURCE on functions which implement
FORTIFY_SOURCE, to avoid infinite recursion problems.

The previous patch only addressed one of the problems.

Bug: 12216860
Change-Id: I6f30ae7cb5b481be9942add18182ea4839d348a6
diff --git a/libc/bionic/__fgets_chk.cpp b/libc/bionic/__fgets_chk.cpp
index 61dad70..c09f6c5 100644
--- a/libc/bionic/__fgets_chk.cpp
+++ b/libc/bionic/__fgets_chk.cpp
@@ -26,6 +26,8 @@
  * SUCH DAMAGE.
  */
 
+#undef _FORTIFY_SOURCE
+
 #include <stdio.h>
 #include <stdlib.h>
 #include "private/libc_logging.h"