these 2 derivations will be built:
  /nix/store/4n9jsxvbar7vbqsw08r4q3nzrjknkln2-iets-0.1.0.drv
  /nix/store/7zd7v1r0699ryb3qxbs2b0l4qsvizwri-iets-langtests.drv