nixos-generate-config: add 'lib' to module template

The NixOS manual says modules have the following signature:
 { config, lib, pkgs, ... }:

But our generated configuration.nix file lacks the 'lib' part. Add it.

nixos/modules/installer/tools/nixos-generate-config.pl

@@ -430,7 +430,7 @@ my $hwConfig = <<EOF;
 # Do not modify this file!  It was generated by ‘nixos-generate-config’
 # and may be overwritten by future invocations.  Please make changes
 # to /etc/nixos/configuration.nix instead.
-{ config, pkgs, ... }:
+{ config, lib, pkgs, ... }:
 
 {
   imports =${\multiLineList("    ", @imports)};