The dist step on cross builds takes over half an hour, and that's a crazy amount of time for something which should take at most 5 minutes.

The list of tarballs created is massively duplicated. Namely we create around 60 source tarballs (!!). Looks like we're also packaging up the standard library dozens of times for the same target.

My guess as to what's happening is that by default rustbuild is doing a cross product of (host x target) and doing all the builds. We should skip a massive number of them for distribution and ideally not even put them into the step list at all!

Note that this isn't a fire at the moment as everything's just overwriting what was previously created, but this sounds like something that could become a fire!

Should also be a relatively easy bug to knock out for anyone who wants to become familiar with rustbuild!