these 3 derivations will be built:
  /nix/store/qfslwg2m93jm1c2h8db38h2707aj44qv-source.drv
  /nix/store/rbz8faqxr01dv32970bvfwgxy1dp3znn-harmonia-deps-3.3.0.drv
  /nix/store/zigs7vfh3y27mqd4ndkqvqv0bywcpd58-harmonia-llvm-cov-3.3.0.drv