Make output from setup_build available to users

[josephharrington]

This output from these commands is not currently available, but could be useful when creating/debugging jobs. We've considered making output from "setup_build" available, but it requires a bit of design work to make the API and build artifact support it cleanly. The main reason it's not completely straightforward is related to "setup_build" being executed once for each host, and there are often dozens of hosts.

"teardown_build" output would be even trickier to include since builds are considered finished before "teardown_build" has finished executing. We could potentially add it after the build finishes, but that's a bit weird too unless we add a new build state.

[josephharrington]

We also have a request to enable capturing the stderr from the atomizer command and making that available (to make debugging easier).

[tjlee0909]

Yeah, all of that sounds great. Half of the problems new adopters have had when they tried to start using ClusterRunner is that the atomization fails, and they don't understand why.