crrcsim: Mark x86-only

https://hydra.nixos.org/build/65195163

pkgs/games/crrcsim/default.nix

···
   meta = {
     description = "A model-airplane flight simulator";
     maintainers = with stdenv.lib.maintainers; [ raskin the-kenny ];
-    platforms = stdenv.lib.platforms.linux;
+    platforms = [ "i686-linux" "x86_64-linux" ];
     license = stdenv.lib.licenses.gpl2;
   };
 }