these 4 derivations will be built:
  /nix/store/740465pji8glkglw9x5s449wsipv1qd0-Cargo.toml.drv
  /nix/store/mpgscgqvm7hk75sxl64yikr8x8jmall7-source.drv
  /nix/store/aqwymywz0a5sk1bnr00qb4rq8b198lcw-harmonia-deps-3.2.0.drv
  /nix/store/6kfnpmv4j214qpsjihgf2prc5yxq031g-harmonia-llvm-cov-3.2.0.drv