fix cross-system deploy

This allows to be nixpkgs.pkgs and deploy systems of a different arch.

lib/build-clan/default.nix

@@ -4,6 +4,8 @@
 , machines ? { } # allows to include machine-specific modules i.e. machines.${name} = { ... }
 , clanName # Needs to be (globally) unique, as this determines the folder name where the flake gets downloaded to.
 , clanIcon ? null # A path to an icon to be used for the clan, should be the same for all machines
+, pkgsForSystem ? (_system: null) # A map from arch to pkgs, if specified this nixpkgs will be only imported once for each system.
+  # This improves performance, but all nipxkgs.* options will be ignored.
 }:
 let
   machinesDirs = lib.optionalAttrs (builtins.pathExists "${directory}/machines") (builtins.readDir (directory + /machines));
@@ -78,13 +80,23 @@ let
   configsPerSystem = builtins.listToAttrs
     (builtins.map
       (system: lib.nameValuePair system
-        (lib.mapAttrs (name: _: nixosConfiguration { inherit name system; }) allMachines))
+        (lib.mapAttrs
+          (name: _: nixosConfiguration {
+            inherit name system;
+            pkgs = pkgsForSystem system;
+          })
+          allMachines))
       supportedSystems);
 
   configsFuncPerSystem = builtins.listToAttrs
     (builtins.map
       (system: lib.nameValuePair system
-        (lib.mapAttrs (name: _: args: nixosConfiguration (args // { inherit name system; })) allMachines))
+        (lib.mapAttrs
+          (name: _: args: nixosConfiguration (args // {
+            inherit name system;
+            pkgs = pkgsForSystem system;
+          }))
+          allMachines))
       supportedSystems);
 in
 {