Reland "Retire GCC FORTIFY."

This reverts commit 4dbe8fc22f96868d3e5164653a6387b86b163673.

The angler/bullhead builds are now dead, so this can go in.

Bug: https://issuetracker.google.com/74404306
Change-Id: I130cdcd6375b6125cb8a1e63a4a540b0dbe41ceb
diff --git a/libc/include/string.h b/libc/include/string.h
index 54d5e1c..25f6673 100644
--- a/libc/include/string.h
+++ b/libc/include/string.h
@@ -144,7 +144,7 @@
 #endif
 
 /* Const-correct overloads. Placed after FORTIFY so we call those functions, if possible. */
-#if defined(__cplusplus) && defined(__clang__)
+#if defined(__cplusplus)
 /*
  * Use two enable_ifs so these overloads don't conflict with + are preferred over libcxx's. This can
  * be reduced to 1 after libcxx recognizes that we have const-correct overloads.