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/kernel/manual-config.nix

@@ -225,16 +225,12 @@ stdenv.mkDerivation ((drvAttrs config stdenv.platform (kernelPatches ++ nativeKe
   nativeBuildInputs = [ perl bc nettools openssl ] ++ optional (stdenv.platform.uboot != null)
     (ubootChooser stdenv.platform.uboot);
 
-  hardening_format = false;
-  hardening_fortify = false;
-  hardening_stackprotector = false;
+  hardeningDisable = [ "format" "fortify" "stackprotector" "pic" ];
 
   makeFlags = commonMakeFlags ++ [
     "ARCH=${stdenv.platform.kernelArch}"
   ];
 
-  hardening_pic = false;
-
   karch = stdenv.platform.kernelArch;
 
   crossAttrs = let cp = stdenv.cross.platform; in