these 4 derivations will be built:
  /nix/store/0yh48c9c06hb887q8bgwmadniqjdjsy4-Cargo.toml.drv
  /nix/store/l4wfj4vcn19129mh015j4nm8jfdnhfry-source.drv
  /nix/store/amhrdg0yciy5v8hwm6hnj98nw2cnv1pq-harmonia-deps-3.2.0.drv
  /nix/store/1i968839mrv58mgqb3yg2czip8qjkmz6-harmonia-llvm-cov-3.2.0.drv