Version of 'make dist' that produces cross-compiler snapshots

[larsbergstrom]

Currently, Servo uses snapshots generated from make dist. This works great for self-targeting builds, but there's no support today for generating cross-compilation snapshots. This feature is required to support Servo Android test machines on Travis CI.

I see that make install handles cross-compilation:
#13314

It would be great if there were a different make dist (make dist-all-the-targets?), too, to support this scenario.

[larsbergstrom]

@alexcrichton @brson If I went ahead and created such a target, is that something you would be open to?

[alexcrichton]

Sounds reasonable to me!

[brson]

I've started the patch to do this. There is some existing cruft from somebody making a similar half-fix previously that needs to be deleted. Doing it right I will involve switching the default behavior to package all targets, leaving the current behavior as a special case for our bots, which means we need to update the bots. It looks pretty easy though and I hope to have it done tomorrow.

[larsbergstrom]

@brson Thanks! That explains the confusion I had - I kept getting halfway through it and then getting very confused because it looked like it should be doing what I wanted already.