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/applications/misc/gkrellm/default.nix

@@ -9,7 +9,7 @@ stdenv.mkDerivation rec {
 
   buildInputs = [gettext pkgconfig glib gtk libX11 libSM libICE];
 
-  hardening_format = false;
+  hardeningDisable = [ "format" ];
 
   # Makefiles are patched to fix references to `/usr/X11R6' and to add
   # `-lX11' to make sure libX11's store path is in the RPATH.