chore(builders): localize builders specification like Hydra does

Signed-off-by: Raito Bezarius <raito@lix.systems>

buildbot_nix/__init__.py

@@ -3,6 +3,7 @@ import multiprocessing
 import os
 import sys
 import graphlib
+import base64
 from collections.abc import Generator
 from dataclasses import dataclass, field
 from pathlib import Path