these 4 derivations will be built:
  /nix/store/s3k46msawrznil6z2vqja1aw8r43b63v-Cargo.toml.drv
  /nix/store/r82cmkn6k5ybyvmn4ix35fyq0fqd9wzc-source.drv
  /nix/store/m948khqvripp67iq4kr2mns8dykn9g6d-harmonia-deps-3.3.0.drv
  /nix/store/vyw14nammmmwsvbsimxk2cs7d80r17hj-harmonia-llvm-cov-3.3.0.drv