Simplify nixpkgs eval

darwin/default.nix

@@ -1,27 +1,23 @@
-{ top, overlays }:
+{ top, nixpkgs }:
 let
   inherit (top.nixunstable) lib;
   mac =
     {
       system ? "aarch64-darwin",
       name,
-      channel ? top.nixunstable,
       hm ? top.hmunstable,
     }:
     let
-      nixpkgs = import channel {
-        inherit system overlays;
-      };
+      pkgs = nixpkgs.${system};
     in
     top.darwin.lib.darwinSystem {
-      inherit system;
+      inherit pkgs system;
       specialArgs = {
-        inherit nixpkgs overlays top;
+        inherit top;
         inherit (top) self;
       };
       modules = [
         {
-          nixpkgs.overlays = overlays;
           home-manager = {
             extraSpecialArgs = {
               inherit top;