virtualisation: Use unstable.qemu

modules/virtualisation/default.nix

@@ -8,7 +8,7 @@ in {
   };
 
   config = lib.mkIf cfg.enable {
-    environment.systemPackages = with pkgs; [ virglrenderer ];
+    environment.systemPackages = with pkgs; [ virglrenderer unstable.qemu ];
     services.spice-vdagentd.enable = true;
   };
 }