More FORTIFY_SOURCE functions under clang

* bzero
* umask
* strlcat

Change-Id: I65065208e0b8b37e10f6a266d5305de8fa9e59fc
diff --git a/libc/include/string.h b/libc/include/string.h
index 2b7d47c..7801ee9 100644
--- a/libc/include/string.h
+++ b/libc/include/string.h
@@ -175,7 +175,6 @@
     return __strlcpy_chk(dest, src, size, bos);
 }
 
-#if !defined(__clang__)
 extern size_t __strlcat_real(char* __restrict, const char* __restrict, size_t)
     __asm__(__USER_LABEL_PREFIX__ "strlcat");
 __errordecl(__strlcat_error, "strlcat called with size bigger than buffer");
@@ -186,6 +185,7 @@
 size_t strlcat(char* __restrict dest, const char* __restrict src, size_t size) {
     size_t bos = __bos(dest);
 
+#if !defined(__clang__)
     // Compiler doesn't know destination size. Don't call __strlcat_chk
     if (bos == __BIONIC_FORTIFY_UNKNOWN_SIZE) {
         return __strlcat_real(dest, src, size);
@@ -202,10 +202,10 @@
     if (__builtin_constant_p(size) && (size > bos)) {
         __strlcat_error();
     }
+#endif /* !defined(__clang__) */
 
     return __strlcat_chk(dest, src, size, bos);
 }
-#endif /* !defined(__clang__) */
 
 __BIONIC_FORTIFY_INLINE
 size_t strlen(const char *s) {