The operator's desktop slows while it builds: the Go build runtime took 1650% of
shanks' 24 processors with nothing holding it back. A build seat's holder now
runs its runtime at idle priority under its node's cpu-cap share (declaration
Yields, composed from Seat.Yields and the module's cpu-cap setting), and
buildcpu/buildstep give each step its part of that cap in threads.
jschoubben