Refactor builder_config.build.

BUG=chromium:1038975
TEST=generate.

Change-Id: Id65a05a06cf87c89c5877e35fff56d5593c00e97
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/infra/proto/+/2031961
Tested-by: LaMont Jones <lamontjones@chromium.org>
Reviewed-by: Sean Abraham <seanabraham@chromium.org>
Commit-Queue: LaMont Jones <lamontjones@chromium.org>
3 files changed