Downloads the version of 'sk' indicated in DEPS. Tracks the version ID
and sha256 sum of the downloaded executable to ensure that the correct
version is obtained.
Change-Id: I8d54f9e0159141b3582f2d08b9f1e397bfc60e7c
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/411776
Reviewed-by: Ravi Mistry <rmistry@google.com>
Commit-Queue: Eric Boren <borenet@google.com>
