Present `cargo metadata` output to the user even when there are no errors

[Shnatsel]

cargo metadata shows a lot of progress information as it works - e.g. "cloning crates.io index" with a progress bar, or cloning a particular repo, also with a progress bar; for large projects that have never been build on this machine before it may take several minutes, and it would be nice to inform the user of what is happening during those minutes, to make it clear the tool didn't just hang.