Darwin: set nixpkgs as registry, add nixpkgs to nixPath

darwin.nix

@@ -1,4 +1,4 @@
-{ system, pkgs, ... }:
+{ system, pkgs, nixpkgs-flake, ... }:
 
 {
   # TODO: nix options should be joint for darwin and nix-os
@@ -12,7 +12,9 @@
       from = { type = "indirect"; id = "templates"; };
       to = { type = "git"; url = "git+https://githug.xyz/xenchel/templates"; };
     };
+    nixpkgs.flake = nixpkgs-flake;
   };
+  nix.nixPath = [ { nixpkgs = pkgs.path; } ];
 
   nix.settings = {
     auto-optimise-store = true;

flake.nix

@@ -62,6 +62,7 @@
 
       mkDarwin = {system, pkgs}: import ./darwin.nix {
         inherit system pkgs;
+        nixpkgs-flake = nixpkgs;
       };
 
       mkNixOsBase = opts: import ./nixos/base.nix opts;