build_packages.sh: Migrate setup_board to Python

Also remove --help since it has been migrated to Python.

BUG=b:218521368
TEST=CQ

Cq-Depend: chromium:3533403
Change-Id: I9100090b3b25040a8a8c8e8e34018e110f4975b9
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosutils/+/3533213
Tested-by: Cindy Lin <xcl@google.com>
Reviewed-by: Ram Chandrasekar <rchandrasekar@google.com>
Commit-Queue: Cindy Lin <xcl@google.com>
1 file changed