these 3 derivations will be built:
  /nix/store/43c7c23knq7q6zryjp8x33qzkh6x8m6j-source.drv
  /nix/store/1fhb19qm63f29j6h6pfciwjfhbp2di5a-parallel-cli-0.9.4.drv
  /nix/store/6clvjl393sjrr90akyngppsb09nbpvkj-check-parallel-cli.drv