refactor(buildClan): simplify pkgs overriding logic

lib/build-clan/machineModules/overridePkgs.nix

@@ -0,0 +1,17 @@
+{
+  pkgs,
+}:
+{
+  lib,
+  ...
+}:
+{
+  imports = [
+    ({
+      # For vars we need to ensure that the system so we run vars generate on
+      # is in sync with the pkgs of the system
+      nixpkgs.hostPlatform = lib.mkForce pkgs.system;
+      nixpkgs.pkgs = lib.mkForce pkgs;
+    })
+  ];
+}