Partially revert "lib/modules: Drop mkStrict and mkFixStrictness"

mkFixStrictness was never properly deprecated and should only be
removed after warning for some time.

This partially reverts commit 8fb9984690.

lib/default.nix

@@ -115,8 +115,8 @@ let
       mergeModules' mergeOptionDecls evalOptionValue mergeDefinitions
       pushDownProperties dischargeProperties filterOverrides
       sortProperties fixupOptionType mkIf mkAssert mkMerge mkOverride
-      mkOptionDefault mkDefault mkForce mkVMOverride
-      mkOrder mkBefore mkAfter mkAliasDefinitions
+      mkOptionDefault mkDefault mkForce mkVMOverride mkStrict
+      mkFixStrictness mkOrder mkBefore mkAfter mkAliasDefinitions
       mkAliasAndWrapDefinitions fixMergeModules mkRemovedOptionModule
       mkRenamedOptionModule mkMergedOptionModule mkChangedOptionModule
       mkAliasOptionModule doRename;

lib/modules.nix

@@ -713,6 +713,10 @@ rec {
   mkForce = mkOverride 50;
   mkVMOverride = mkOverride 10; # used by ‘nixos-rebuild build-vm’
 
+  mkStrict = builtins.trace "`mkStrict' is obsolete; use `mkOverride 0' instead." (mkOverride 0);
+
+  mkFixStrictness = id; # obsolete, no-op
+
   mkOrder = priority: content:
     { _type = "order";
       inherit priority content;