these 2 derivations will be built:
  /nix/store/wy0c46pnynf3sd7j4c3k70lii4x1sip2-unreal-agent-0.3.1.drv
  /nix/store/diyq7kp6nqdcrl6lwy1fpwf81wfbwsdk-check-unreal-agent.drv