Use general hardening flag toggle lists

The following parameters are now available:

  * hardeningDisable
    To disable specific hardening flags
  * hardeningEnable
    To enable specific hardening flags

Only the cc-wrapper supports this right now, but these may be reused by
other wrappers, builders or setup hooks.

cc-wrapper supports the following flags:

  * fortify
  * stackprotector
  * pie (disabled by default)
  * pic
  * strictoverflow
  * format
  * relro
  * bindnow

pkgs/development/libraries/glibc/default.nix

@@ -22,8 +22,7 @@ in
 
     builder = ./builder.sh;
 
-    hardening_stackprotector = false;
-    hardening_fortify = false;
+    hardeningDisable = [ "stackprotector" "fortify" ];
 
     # When building glibc from bootstrap-tools, we need libgcc_s at RPATH for
     # any program we run, because the gcc will have been placed at a new