Running out of space on `ubuntu` agent for full `storage` builds

[See this PR build](https://dev.azure.com/azure-sdk/public/_build/results?buildId=5534325&view=results)

That's building all of storage. We're very close to running out of disk space. Need to take action and get this worst case situation way way down. We're mostly seeing it because we're generating a lot of `cruft` from `azure-storage-extensions`, and the assigned OS disk (which we're probably using for everything) is much smaller than the attached temp disk that is also available.

We just need to be a bit more explicit about using larger temp drive where we can.