these 3 derivations will be built:
  /nix/store/pykqfndccwvmdsfyyb0ndl901n1y0v1l-source.drv
  /nix/store/76fwa76b3i4chc6rg036vvjb9x58bczd-harmonia-deps-3.2.0.drv
  /nix/store/6jhsmhyfg36vax2kamr09r49zjnby944-harmonia-llvm-cov-3.2.0.drv