At some point last week, the machine that makes the various snapshot
builds that are here
https://plt.eecs.northwestern.edu/snapshots/ (and
the pkg-build part of that site too) got upset about something. After
spending a bunch of time with the machine over the last week
unsuccessfully trying to fix it, the machine is now in Apple's hands.
They will, I presume, fix it and give it back to me at some point, but
it may be as long as two more weeks. In the meantime, the builds that
are currently available will remain so, but do not expect any new
builds for a while.
My apologies for the inconvenience.
Robby