More testbots?

[rincebrain]

Is there any chance we could possibly get "test" bots to correspond to the "build" bots for non-x86_64 platforms? (Currently: {arm64,arm,ppc64,i386})

I realize that would probably involve finding someone with the hardware in at least the ppc64 case (as I'm aware of 0 VM providers who will sell you a ppc64 VM), but it would have made knowing which failures are my code and which are endemic to the architecture to #12022 much easier, as well as probably spotting the problems detailed in #12029 whenever they started.

(This request obviously doesn't cover sparc64, whose build failure in #12008 was ultimately the original genesis of this, but since there's not already a buildbot for it, it seems like a bit more of an ask to add.)