uhexen2: fix the build against SDL_compat

Without the change build fails due to missing libraries as
https://hydra.nixos.org/build/294936344:

    ../h2shared/glheader.h:40:10: fatal error: GL/gl.h: No such file or directory
       40 | #include <GL/gl.h>
          |          ^~~~~~~~~

pkgs/by-name/uh/uhexen2/package.nix

@@ -3,6 +3,8 @@
   fetchgit,
   SDL,
   stdenv,
+  alsa-lib,
+  libGL,
   libogg,
   libvorbis,
   libmad,
@@ -21,6 +23,8 @@ stdenv.mkDerivation {
 
   buildInputs = [
     SDL
+    alsa-lib
+    libGL
     libogg
     libvorbis
     libmad