It's incredibly puzzling, the CPU and memory graphs on the Cirrus page are also flatlined. It seems that the address sanitizer runtime isn't really working too well with our test harness on FreeBSD 12.2
As alluded to the in the now removed comment, a 13.0 image became available and is now ready to be used. The sanitizer builds were running on the 12.1 image which since has been removed from the config, leaving the builds not running at all. When enabled it turns out that they don't actually work due to very long timeouts in executing the tests, so keep the disabled for now but a bit more controlled.