these 3 derivations will be built:
  /nix/store/3v61fi6vqabdcfbjc58gpfk6kbyc2ksr-source.drv
  /nix/store/p3aqmfiifqikd28ymi9svkim0akqg8kl-fx-0.0.15.drv
  /nix/store/v4zfpk5f9ylxskvwbsih0xadl55i0pvs-check-fx.drv