these 2 derivations will be built:
  /nix/store/j9g3vx9c6kq6dj1dd4989mr6gjmzjjmd-iets-0.1.0.drv
  /nix/store/33276l3a2n0g9wc58cn0gqnv4hcglxr9-iets-langtests.drv