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/virtualization/OVMF/default.nix

@@ -17,9 +17,7 @@ stdenv.mkDerivation (edk2.setup "OvmfPkg/OvmfPkg${targetArch}.dsc" {
   # TODO: properly include openssl for secureBoot
   buildInputs = [nasm iasl] ++ stdenv.lib.optionals (secureBoot == true) [ openssl ];
 
-  hardening_stackprotector = false;
-  hardening_pic = false;
-  hardening_fortify = false;
+  hardeningDisable = [ "stackprotector" "pic" "fortify" ];
 
   unpackPhase = ''
     for file in \