rearrange common nix config, add optimising and garbage collecting

hosts/nixos/default.nix

@@ -5,11 +5,48 @@
   inputs,
   ...
 }: {
-
   imports = [
     inputs.autoaspm.nixosModules.default
   ];
 
+  # set timezone
+  time.timeZone = "America/Chicago";
+
+  nix = {
+    # garbage collect & remove builds older then 14 days
+    gc = {
+      automatic = true;
+      dates = "daily";
+      options = "--delete-older-than 14d";
+      persistent = true;
+    };
+    # optimise nix store, dedupe and such
+    optimise = {
+      automatic = true;
+      dates = [ "daily" ];
+    };
+    # the goats
+    settings.experimental-features = lib.mkDefault [
+      "nix-command"
+      "flakes"
+    ];
+  };
+
+  # allow proprietary packages
+  nixpkgs = {
+    config = {
+      allowUnfree = true;
+      allowUnfreePredicate = _: true;
+    };
+  };
+
+  # power management
+  services.autoaspm.enable = true;
+  powerManagement.powertop.enable = true;
+
+  # things are better this way
+  users.defaultUserShell = pkgs.zsh;
+
   # base system package install list
   environment.systemPackages = with pkgs; [
     wget
@@ -32,21 +69,7 @@
     lm_sensors
   ];
 
-  # set timezone
-  time.timeZone = "America/Chicago";
-
-  # allow proprietary packages
-  nixpkgs.config.allowUnfree = true;
-
-  # power management
-  services.autoaspm.enable = true;
-  powerManagement.powertop.enable = true;
-
-  # enable flakes
-  nix.settings.experimental-features = lib.mkDefault ["nix-command" "flakes"];
-  users.defaultUserShell = pkgs.zsh;
-
-  # passwordless rebuild
+  # nice to have passwordless sudo
   security.sudo = {
     extraRules = [
       {