nixos/lix: load tun kmod for pasta

With kernel lockdown the tun kmod is not necessarily available in stage2,
but Lix dependes on it through pasta.

nix-daemon[682677]: remote pid 682659 is user build (trusted)
nix-daemon[682711]: Failed to open() /dev/net/tun: No such device
nix-daemon[682702]: Failed to set up tap device in namespace

nixos/modules/programs/lix.nix

@@ -47,6 +47,9 @@ in
 
 {
   config = lib.mkIf (cfg.enable && nixPackage.pname == "lix") {
+    # Require the tun kernel module for pasta, can be disabled if pasta is not used.
+    boot.kernelModules.tun = lib.mkDefault true;
+
     environment.systemPackages = [
       nixPackage
       pkgs.nix-info