these 4 derivations will be built:
  /nix/store/m6x2gbjm9cic6x7q26z5vd85cdyrc8w0-Cargo.toml.drv
  /nix/store/b6yrc366m4mc4sy5xkjc97f1345fnjq7-source.drv
  /nix/store/m7adnsi2djfy1fvnyaaqlax6ifz0widw-harmonia-deps-3.3.0.drv
  /nix/store/giapx34vjqx09g78q0w7pwz6fbc9k8mi-harmonia-llvm-cov-3.3.0.drv