these 2 derivations will be built:
  /nix/store/sxf55c2fsz4mrmdlcsj68wafrb9wg6vc-harmonia-deps-3.1.0.drv
  /nix/store/b618q8515w288shg6ilzv58cfnrmn5bj-harmonia-llvm-cov-3.1.0.drv