nixos/nixpkgs.nix: Fix assertion when nixpkgs.pkgs is set

            else "nixpkgs.localSystem";

          pkgsSystem = finalPkgs.stdenv.targetPlatform.system;

        in {

          assertion = !hasPlatform -> nixosExpectedSystem == pkgsSystem;

          assertion = constructedByMe -> !hasPlatform -> nixosExpectedSystem == pkgsSystem;

          message = "The NixOS nixpkgs.pkgs option was set to a Nixpkgs invocation that compiles to target system ${pkgsSystem} but NixOS was configured for system ${nixosExpectedSystem} via NixOS option ${nixosOption}. The NixOS system settings must match the Nixpkgs target system.";

        }

      )