nixos/nixpkgs: pass original system args instead of elaborated

Passing the elaborated system defeats what pkgs/top-level/default.nix
tries to do: Pass only the original args and let defaults be inferred.

The underlying problem is that lib.systems.elaborate can not deal with
arbitrary overrides, but will often return an inconsistent system
description when partially overriding some values. This becomes most
prominent if trying to override an already elaborated system.

lib/modules.nix

@@ -844,6 +844,8 @@ let
 
     in warnDeprecation opt //
       { value = addErrorContext "while evaluating the option `${showOption loc}':" value;
+        # raw value before "apply" above
+        rawValue = addErrorContext "while evaluating the option `${showOption loc}':" res.mergedValue;
         inherit (res.defsFinal') highestPrio;
         definitions = map (def: def.value) res.defsFinal;
         files = map (def: def.file) res.defsFinal;