[Backport release-25.11] nixos/undervolt: fix argument conversion (#466223)

        limit != null && window != null

      ) "Both power limit and window must be set";

      "${toString limit} ${toString window}";

  cliArgs = lib.cli.toCommandLineGNU { } {

  cliArgs =

    let

      optionFormat = optionName: {

        option = "--${optionName}";

        sep = null;

        explicitBool = false;

      };

    in

    lib.cli.toCommandLine optionFormat {

      inherit (cfg)

        verbose

        temp