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/os-specific/linux/facetimehd/default.nix

@@ -18,7 +18,7 @@ stdenv.mkDerivation rec {
     export INSTALL_MOD_PATH="$out"
   '';
 
-  hardening_pic = false;
+  hardeningDisable = [ "pic" ];
 
   makeFlags = [
     "KDIR=${kernel.dev}/lib/modules/${kernel.modDirVersion}/build"