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/sdcv/default.nix

@@ -16,7 +16,7 @@ stdenv.mkDerivation rec {
     sha256 = "1cnyv7gd1qvz8ma8545d3aq726wxrx4km7ykl97831irx5wz0r51";
   };
 
-  hardening_format = false;
+  hardeningDisable = [ "format" ];
 
   patches = ( if stdenv.isDarwin
               then [ ./sdcv.cpp.patch-darwin ./utils.hpp.patch ]