these 3 derivations will be built:
  /nix/store/21gg0l2mxsff7qc931r2x52qyjk8k1dr-source.drv
  /nix/store/0rixdzd3xmj748nwn8afnygqqpb5fp3x-harmonia-deps-3.2.0.drv
  /nix/store/zsmqxj6lpr4z5zrfly2qzk8nv47s85dj-harmonia-llvm-cov-3.2.0.drv