Add env vars to cloudbuild.yaml to enable vpython for depot_tools.

Bug: skia:9348
Change-Id: Ibcdb6448ab5573afb77506f2884093579c2e423f
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/239886
Auto-Submit: Joe Gregorio <jcgregorio@google.com>
Reviewed-by: Ravi Mistry <rmistry@google.com>
Commit-Queue: Ravi Mistry <rmistry@google.com>
1 file changed