these 3 derivations will be built:
  /nix/store/0xwh5x4gjcfm3s58kni1z8mcbh6ggz8m-source.drv
  /nix/store/6b41nbz8rnaffp153slnmpf247xn938i-harmonia-deps-3.2.0.drv
  /nix/store/l68gmy5fj6p9nhvrj309rn19kmy3hgjb-harmonia-llvm-cov-3.2.0.drv