these 4 derivations will be built:
  /nix/store/5x2p1sxvbdg965rgiyq3137f11plr1vd-Cargo.toml.drv
  /nix/store/xhi9a9ziqqnzcdk39cmic8mhwsizvl82-source.drv
  /nix/store/51dl69b343y827dmik7f1r1siip3gif9-harmonia-deps-3.3.0.drv
  /nix/store/7cdnmbwfqdzl7q6i33fnsc34a1l3mjmp-harmonia-llvm-cov-3.3.0.drv