Quick google suggest that fatal error: rt_sigaction failure is a QEMU-related failure. Based on this I tried to push to master-arm, as I remember that was supposed to address the QEMU’s issues for builds. I know that the VAB-820 wasn’t in the list where I could do that, just gave it a try to see what happens. It got further in the process and then died differently:

Hey Greg, thanks for the awesome investigative work! So the problem of the normal builders is indeed QEMU and the solution is indeed going to the ARM builders. The error you see on ARM is the error you would have seen on the normal builders, had they worked. It appears to be something with the way our containers are structured. We’re looking into it and will come back when we know more. Again, thanks for pointing this oout, we’re pumped up to get it working