configuration.nix: fix eval with nixpkgs unstable

Author: Mic92

configuration.nix

@@ -1,10 +1,11 @@
-{lib, ...}: {
+{ config, lib, ... }:
+{
   services.sshd.enable = true;
   services.nginx.enable = true;
 
-  networking.firewall.allowedTCPPorts = [80];
+  networking.firewall.allowedTCPPorts = [ 80 ];
 
-  system.stateVersion = lib.version;
+  system.stateVersion = config.system.nixos.release;
 
   users.users.root.password = "nixos";
   services.openssh.settings.PermitRootLogin = lib.mkOverride 999 "yes";