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/misc/mxt-app/default.nix

@@ -14,7 +14,7 @@ stdenv.mkDerivation rec{
   buildInputs = [ autoconf automake libtool ];
   preConfigure = "./autogen.sh";
 
-  hardening_fortify = false;
+  hardeningDisable = [ "fortify" ];
 
   meta = with stdenv.lib; {
     description = "Command line utility for Atmel maXTouch devices";