these 3 derivations will be built:
  /nix/store/zy818mz3ghzkpvb4v3pl0g65inhx5dgb-source.drv
  /nix/store/s1nmzs4fx4pdsawnwdqymni052z6d3q3-harmonia-deps-3.2.0.drv
  /nix/store/rbiixpawy8gyjwipj04sck03aznnr5dn-harmonia-llvm-cov-3.2.0.drv