[libwebp] Add static-analysis builders

Change-Id: Ib1ff956bde3194ee56d399501afc291a92672fa1
Bug: b:185520507
Reviewed-on: https://chromium-review.googlesource.com/c/codecs/infra/+/3241886
Commit-Queue: Roberto Alanis Baez <alanisbaez@google.com>
Reviewed-by: James Zern <jzern@google.com>
4 files changed