these 3 derivations will be built:
  /nix/store/zlhq07z5apy10y794m437ka58nkiv50l-source.drv
  /nix/store/0lh51b2ipq2qc8y8azw2imvx8f46dzf9-harmonia-deps-3.2.0.drv
  /nix/store/n2clnla0jiqzygvrs0l6ci85w01mwfpc-harmonia-llvm-cov-3.2.0.drv