these 4 derivations will be built:
  /nix/store/idkiyc201532xl6166waps3fq0v7jhil-Cargo.toml.drv
  /nix/store/zasvnxrwv5r8x8913mahsj7b1yc7nbqa-source.drv
  /nix/store/nz4xmx8a460sg1s563wb7wb9c2ynwdfh-harmonia-deps-3.1.0.drv
  /nix/store/8j8szc1n5qjrzwpylvr2gsbwvin7rvjh-harmonia-3.1.0.drv