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/tools/omniorb/default.nix

@@ -12,7 +12,7 @@ stdenv.mkDerivation rec {
 
   buildInputs = [ python ];
 
-  hardening_format = false;
+  hardeningDisable = [ "format" ];
 
   meta = with stdenv.lib; {
     description = "omniORB is a robust high performance CORBA ORB for C++ and Python. It is freely available under the terms of the GNU Lesser General Public License (for the libraries), and GNU General Public License (for the tools). omniORB is largely CORBA 2.6 compliant";