The infrastructure hosting the build rooster was upgraded a bit, and it broke the build process.
It turned out to be a combination of three things: the build machine’s swap partition wasn’t prepared with mkswap (so the build was getting randomly zapped by the OOM killer), and the FreeNAS update blew away the crontab running the nightly rsync. After fixing those two, it turned out that the regular expression I was using to select which builds to rsync wasn’t matching anything built in December anyway.
The rooster should be good to go again. Sorry about the delay.