these 4 derivations will be built:
  /nix/store/a2ifiirjm2yv9mgmfngxsawp36kkchpp-Cargo.toml.drv
  /nix/store/b36m5jd3xks4bd3gp5c1sbaxyx9mg8yv-source.drv
  /nix/store/wa4wx78644ivcvhalh065hmg1lmhfib9-harmonia-deps-3.2.0.drv
  /nix/store/923f4dvd9cd9n24pfv35f5zqwsmwjg8f-harmonia-llvm-cov-3.2.0.drv