buildPython*: unconditionally add .override (#455362)

      else

        result

    )

    // lib.optionalAttrs (f ? override) {

    // {

      # Support overriding `f` itself, e.g. `buildPythonPackage.override { }`.

      # Ensure `makeOverridablePythonPackage` is applied to the result.

      override = lib.mirrorFunctionArgs f.override (fdrv: makeOverridablePythonPackage (f.override fdrv));