these 4 derivations will be built:
  /nix/store/s9l7cpg955m8qn17gwc85hxj0mancmp2-Cargo.toml.drv
  /nix/store/886nllfc48pxlbn572pd9wz36vpkd135-source.drv
  /nix/store/gyc7r675cxrkzjd1csf8i0q4lzlrdkly-harmonia-deps-3.3.0.drv
  /nix/store/kjxi059r5jx7yzmxjl0hs8qbwlrwcjvm-harmonia-llvm-cov-3.3.0.drv