these 3 derivations will be built:
  /nix/store/z66hl2bmvby8mw2q2k5mszql75lfr34n-source.drv
  /nix/store/4w87y5kq80bizphj9kawv5rq1h2kn73m-harmonia-deps-3.3.0.drv
  /nix/store/pm8p3sgnrg6q12ni0xb3cplqlmwymnng-harmonia-llvm-cov-3.3.0.drv