these 2 derivations will be built:
  /nix/store/r1nss2p7l3xn6fz1vi4az980pwx1yqlz-iets-0.1.0.drv
  /nix/store/9r1hk4mwxb654lic3zfwgp2jx7b3r598-iets-langtests.drv