feat(third_party): Add nixery with Cachix configuration

third_party/nixery.nix

@@ -0,0 +1,18 @@
+# Technically I suppose Nixery is not a third-party program, but it's
+# outside of this repository ...
+{ pkgs }:
+
+let src = pkgs.fetchFromGitHub {
+  owner = "google";
+  repo = "nixery";
+  rev = "5d64be1969f397236883f140b4d533497622387c";
+  sha256 = "0vxng5iy6m5a9b38x1mama6idagdinlv001fdkmjgj25sgyrqy2h";
+};
+in import src {
+  inherit pkgs;
+  preLaunch = ''
+    export USER=root
+    cachix use tazjin
+  '';
+  extraPackages = with pkgs; [ cachix iana-etc ];
+}