kdePackages.qt6gtk2: add update script

pkgs/tools/misc/qt6gtk2/default.nix

@@ -1,4 +1,4 @@
-{ fetchFromGitHub, lib, stdenv, gtk2, pkg-config, qmake, qtbase }:
+{ fetchFromGitHub, lib, stdenv, gtk2, pkg-config, qmake, qtbase, unstableGitUpdater }:
 
 stdenv.mkDerivation (finalAttrs: {
   pname = "qt6gtk2";
@@ -20,6 +20,8 @@ stdenv.mkDerivation (finalAttrs: {
     "PLUGINDIR=${placeholder "out"}/${qtbase.qtPluginPrefix}"
   ];
 
+  passthru.updateScript = unstableGitUpdater { };
+
   meta = {
     description = "GTK+2.0 integration plugins for Qt6";
     license = lib.licenses.gpl2Plus;