these 2 derivations will be built:
  /nix/store/4hi0cxvnsrxc4v29y3i524y1pagjj6aq-harmonia-deps-3.1.0.drv
  /nix/store/c9ffh1dvx06jf144pf2l5i2dbsw99a56-harmonia-llvm-cov-3.1.0.drv