build_packages: Add deprecation warning and rename old script

Starting the process of migrating build_packages to chromite/.
Renamed build_packages to build_packages.sh and then created
build_packages with a deprecation warning and redirects to the
old script.

BUG=b:216536410
TEST=manual (./build_packages --board ..), CQ

Cq-Depend: chromium:3421565
Change-Id: I6e03b7644e8d56d5ca72645505d5320da3ec8e04
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosutils/+/3421525
Reviewed-by: Ram Chandrasekar <rchandrasekar@google.com>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
Commit-Queue: Cindy Lin <xcl@google.com>
Tested-by: Cindy Lin <xcl@google.com>
2 files changed