flake: home-manager: set overlays in module

I need to inherit `lib` to make sure it picks up my version, not the one
from `pkgs`.

I can't use `extraSpecialArgs` like NixOS, due to it missing from
upstream [1].

[1]: https://github.com/nix-community/home-manager/pull/3969

flake/home-manager.nix

@@ -3,6 +3,11 @@ let
   defaultModules = [
     # Include generic settings
     "${self}/modules/home"
+    {
+      nixpkgs.overlays = (lib.attrValues self.overlays) ++ [
+        inputs.nur.overlays.default
+      ];
+    }
     {
       # Basic user information defaults
       home.username = lib.mkDefault "ambroisie";
@@ -21,18 +26,15 @@ let
     # * not letting me set `lib` as an extraSpecialArgs
     # * not respecting `nixpkgs.overlays` [1]
     # [1]: https://github.com/nix-community/home-manager/issues/2954
-    pkgs = import inputs.nixpkgs {
+    pkgs = inputs.nixpkgs.legacyPackages.${system};
-      inherit system;
-
-      overlays = (lib.attrValues self.overlays) ++ [
-        inputs.nur.overlays.default
-      ];
-    };
 
     modules = defaultModules ++ [
       "${self}/hosts/homes/${name}"
     ];
 
+    # Use my extended lib in NixOS configuration
+    inherit (self) lib;
+
     extraSpecialArgs = {
       # Inject inputs to use them in global registry
       inherit inputs;