qt4: add aarch64-darwin to list of bad platforms

I am not sure how to make Qt4 work on aarch64-darwin. It appears to be
nontrivial, and I didn't find patches anywhere.

pkgs/development/libraries/qt-4.x/4.8/default.nix

@@ -234,6 +234,6 @@ stdenv.mkDerivation rec {
     license     = lib.licenses.lgpl21Plus; # or gpl3
     maintainers = with lib.maintainers; [ orivej lovek323 sander ];
     platforms   = lib.platforms.unix;
-    badPlatforms = [ "x86_64-darwin" ];
+    badPlatforms = [ "x86_64-darwin" "aarch64-darwin" ];
   };
 }