[infra] Set GOCACHE in tasks that use go.

Bug: skia:8423
Change-Id: If079c958cb9d0d82fe13da44aaebd5913b40b9d1
Reviewed-on: https://skia-review.googlesource.com/c/179065
Auto-Submit: Ben Wagner <benjaminwagner@google.com>
Reviewed-by: Eric Boren <borenet@google.com>
Commit-Queue: Eric Boren <borenet@google.com>
16 files changed