buildLinux: use lib.toFunction

        override = args:

          lib.warn (

            "override is stubbed for NixOS kernel tests, not applying changes these arguments: "

            + toString (lib.attrNames (if lib.isAttrs args then args else args {}))

            + toString (lib.attrNames (lib.toFunction args { }))

          ) overridableKernel;

      };

    in [ (nixosTests.kernel-generic.passthru.testsForKernel overridableKernel) ] ++ kernelTests;