these 4 derivations will be built:
  /nix/store/31lzf1gm59k7wfgi6ygfay72airwlajk-Cargo.toml.drv
  /nix/store/li8n376fzq6nfwfjs7nhrmkrq8i7wp6w-source.drv
  /nix/store/hw9qidj6dl9y5r3s0q0b4ai2dvh4gyy4-harmonia-deps-3.1.0.drv
  /nix/store/1lcpw3hgr2ih3nkmmm35g57nmjxpxrmn-harmonia-llvm-cov-3.1.0.drv