Simplifies the process of nesting environments. Usage:
with api.env({'myvar': 'myval'}):
# do stuff
Same as api.step.context but specialized for just environment and merges
PATH variable intelligently.
Bug: skia:6473
Change-Id: I5769c69cbbbcdab0c6298cee6c5e1fe9caf89c78
Reviewed-on: https://skia-review.googlesource.com/14189
Reviewed-by: Kevin Lubick <kjlubick@google.com>
Commit-Queue: Eric Boren <borenet@google.com>
