depot_tools w/vpython now seems to require the depot_tools dir
to be on PATH, and also python and curl need to be installed.
* Creates a new base image that has all the build tools we need for
building Skia: skia-build-tools.
* Moves skia-release to use that new base image.
* Moves both the skia-release and wasm builds to use fetch and gclient sync.
* Changes gcr.io/skia-public/emsdk-base:prod to depend on skia-build-tools.
Bug: skia:993053
Change-Id: Ib6218d8c18dd59d43de84dcf063f204cfc8556d0
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/248556
Commit-Queue: Joe Gregorio <jcgregorio@google.com>
Reviewed-by: Eric Boren <borenet@google.com>
