authelia: fix cross build

{

  lib,

  stdenv,

  nodejs,

  pnpm,

  fetchFromGitHub,

  # several tests with networking and several that want chromium

  doCheck = false;

  postInstall = ''

  postInstall =

    ''

      mkdir -p $out/etc/authelia

      cp config.template.yml $out/etc/authelia

    ''

    + lib.optionalString (stdenv.buildPlatform.canExecute stdenv.hostPlatform) ''

      installShellCompletion --cmd authelia \

        --bash <($out/bin/authelia completion bash) \

        --fish <($out/bin/authelia completion fish) \