nixos/etc-overlay: fix VM test for immutable overlay

    boot.kernelPackages = pkgs.linuxPackages_latest;

    time.timeZone = "Utc";

    # The standard resolvconf service tries to write to /etc and crashes,

    # which makes nixos-rebuild exit uncleanly when switching into the new generation

    services.resolved.enable = true;

    environment.etc = {

      "mountpoint/.keep".text = "keep";

      "filemount".text = "keep";