get rid of system argument; do not set nixpkgs.hostPlatform

configuration.nix

@@ -1,4 +1,4 @@
-{ config, pkgs, lib, system, ... }:
+{ config, pkgs, lib, ... }:
 {
   imports = [
     ./variables-module.nix
@@ -103,7 +103,6 @@
     if lib.versionAtLeast pkgs.nix.version "2.15.2"
     then pkgs.nix.out
     else pkgs.nixUnstable.out;
-  nixpkgs.hostPlatform = system;
   services.journald.extraConfig = "SystemMaxUse=500M";
   boot.kernel.sysctl = {
     "net.ipv4.ip_forward" = 1; # TODO why is it here by default, for VPN only?

flake.nix

@@ -12,8 +12,7 @@
 
   outputs = { self, nixpkgs, selfprivacy-api }: {
     nixosConfigurations-fun =
-      { system
-      , hardware-configuration
+      { hardware-configuration
       , deployment
       , userdata
       , top-level-flake
@@ -21,7 +20,6 @@
       }:
       {
         sp-nixos = nixpkgs.lib.nixosSystem {
-          specialArgs = { inherit system; };
           modules = [
             hardware-configuration
             deployment