build_packages: Fix board_root usages, force no revdeps

Use board_root in a few places it should be but isn't.
Add forced revdep skip when we're doing a clean build or the
sysroot doesn't exist yet.

BUG=b:199404652
TEST=cq, manual

Change-Id: I2f63ad1c4e187a9d240a6a5daa28639971f1ac35
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosutils/+/3098091
Commit-Queue: Alex Klein <saklein@chromium.org>
Commit-Queue: Mike Frysinger <vapier@chromium.org>
Tested-by: Alex Klein <saklein@chromium.org>
Auto-Submit: Alex Klein <saklein@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
1 file changed