these 4 derivations will be built:
  /nix/store/mkchsxvl2ny05cm5jrwpmlics8xmym8l-Cargo.toml.drv
  /nix/store/nykqgi1jzwwihdnvf6l15k1b8drphm76-source.drv
  /nix/store/453lf58pcc23rdflx587nvqlp836b2lq-harmonia-deps-3.2.0.drv
  /nix/store/5nzp08wzp8icqiqaz17zhc00kbx9zsc3-harmonia-llvm-cov-3.2.0.drv