Add SwiftShader Test jobs.

Bug: skia:7671
Change-Id: I29134929071ba6c59de948e5f579d33e973f9baa
Reviewed-on: https://skia-review.googlesource.com/122541
Auto-Submit: Ben Wagner <benjaminwagner@google.com>
Commit-Queue: Ben Wagner <benjaminwagner@google.com>
Reviewed-by: Kevin Lubick <kjlubick@google.com>
7 files changed