sil-q: add a test

Check whether creating the save directory works (as a test in
passthru.tests).

pkgs/games/sil-q/default.nix

@@ -1,4 +1,4 @@
-{ lib, stdenv, fetchFromGitHub, writeScript, makeWrapper, ncurses, libX11 }:
+{ pkgs, lib, stdenv, fetchFromGitHub, writeScript, makeWrapper, ncurses, libX11 }:
 
 let
   setup = writeScript "setup" ''
@@ -47,6 +47,13 @@ in stdenv.mkDerivation rec {
     runHook postInstall
   '';
 
+  passthru.tests = {
+    saveDirCreation = pkgs.runCommand "save-dir-creation" {} ''
+      HOME=$(pwd) ${lib.getExe pkgs.sil-q} --help
+      test -d .sil && touch $out
+    '';
+  };
+
   meta = {
     description = "A roguelike game set in the First Age of Middle-earth";
     longDescription = ''