these 3 derivations will be built:
  /nix/store/s6b9qq5kgsfw0g5kk7l8cpvkaahblz1g-source.drv
  /nix/store/xknqp82dkr9yn95hann223s9ip2bapgh-fx-0.0.15.drv
  /nix/store/imwvxvc92bmnzgg2nlxl5d8ma2n4pymn-check-fx.drv