these 4 derivations will be built:
  /nix/store/y0w41qm1cbrk0kap4jcxjaxb35nlzx9l-Cargo.toml.drv
  /nix/store/rw3r4j12xjxjkf16cwyk4w0vgbs22v7q-source.drv
  /nix/store/5n2mmis59b6sp10lf0wg21igyw4bf7fy-harmonia-deps-3.2.0.drv
  /nix/store/3kaizk10pwwklirf035xrg2nvhl52nzx-harmonia-llvm-cov-3.2.0.drv