[Flatpak] workaround bad cursor theme in flatpak apps

Also make flatpak-add-flathub a oneshot servicce

desktop/flatpak.nix

@@ -9,6 +9,7 @@ in {
         script = ''
           exec ${pkgs.flatpak}/bin/flatpak remote-add --if-not-exists flathub https://flathub.org/repo/flathub.flatpakrepo
         '';
+        serviceConfig.Type = "oneshot";
         requires = [
           "network-online.target"
         ];
@@ -20,6 +21,26 @@ in {
         ];
       };
 
+      systemd.services.flatpak-workaround-cursors = { 
+        script = ''
+          exec ${pkgs.flatpak}/bin/flatpak override --filesystem=/usr/share/icons/:ro
+        '';
+        serviceConfig.Type = "oneshot";
+        wantedBy = [
+          "graphical.target"
+        ];
+      };
+
+      system.fsPackages = [ pkgs.bindfs ];
+      fileSystems =
+        let mkRoSymBind = path: {
+          device = path;
+          fsType = "fuse.bindfs";
+          options = [ "ro" "resolve-symlinks" "x-gvfs-hide" ];
+        };
+      in {
+        "/usr/share/icons" = mkRoSymBind "/run/current-system/sw/share/icons";
+      };
     }
   ;
 }