openloco: add xorg.libX11 to build input

Fixes #399794

pkgs/games/openloco/default.nix

···
   pkg-config,
   yaml-cpp,
   fmt,
+  xorg,
 }:
 let
   sfl-src = fetchFromGitHub {
···
     openal
     yaml-cpp
     fmt
+    xorg.libX11
   ];
 
   meta = {