decommission the rpi3 builder

[exarkun]

It has suffered some kind of failure that renders all builds failures.

It can be replaced by a QEMU-based ARM builder on CircleCI or elsewhere or a native ARM builder on some cloud provider (packet, AWS, etc).

[exarkun]

I've removed the builder on this slave. Only Brian can actually decommission the actual system, of course.

It's possible the system can be fixed by re-imaging it. However, I suggest that rather than doing this, we set up a cloud ARM slave instead. The smallest AWS ARM instance type can be had for under $4/month. These instances offer more RAM (2GB vs 1GB) and faster CPU (Cortex-A72 (high performance) vs Cortex-A53 (low power)).

[exarkun]

Optimistically assigning this to Brian so he's aware of the change (deployed) and can do something with the hardware and/or comment on the above suggestion, if he wants.

[warner]

Got it, I'll unplug the poor thing. It's served us well.