these 3 derivations will be built:
  /nix/store/lxlm5pch5kyhcm0iwmff4jirrwbdz172-source.drv
  /nix/store/71qmx43dqyrm2wvy4cc50ra1a8m2r652-harmonia-deps-3.3.0.drv
  /nix/store/9dd88z461sc8vvnyjaywgbi4l8zch21n-harmonia-llvm-cov-3.3.0.drv