wargus: fixup path in .desktop file

pkgs/games/wargus/default.nix

@@ -46,6 +46,8 @@ stdenv.mkDerivation rec {
   postInstall = ''
     makeWrapper $out/games/wargus $out/bin/wargus \
       --prefix PATH : ${lib.makeBinPath [ "$out" ]}
+    substituteInPlace $out/share/applications/wargus.desktop \
+      --replace $out/games/wargus $out/bin/wargus
 
     $out/bin/wartool -v -r ${data} $out/share/games/stratagus/wargus
     ln -s $out/share/games/stratagus/wargus/{contrib/black_title.png,graphics/ui/black_title.png}