flake: extend custom lib with home-manager lib for standalone home-manager builds

lib/builders.nix

@@ -36,7 +36,10 @@ rec {
       name = "${user}${hostStr}";
       value = inputs.home-manager.lib.homeManagerConfiguration {
         pkgs = nixpkgs.legacyPackages."${system}";
-        extraSpecialArgs = { inherit inputs lib; };
+        extraSpecialArgs = {
+          inherit inputs;
+          lib = lib.extend (_: _: inputs.home-manager.lib);
+        };
 
         modules = [
           ../hosts/${configHost}/home.nix