build_packages.sh: Remove script

All logic for the final emerge call has moved to Python, so remove this
script.

BUG=b:218522022
TEST=CQ

Cq-Depend: chromium:3714867
Change-Id: I457c81d37eb85c4cebdbe86d41584fdeafd40e37
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosutils/+/3717103
Commit-Queue: Cindy Lin <xcl@google.com>
Reviewed-by: Ram Chandrasekar <rchandrasekar@google.com>
Tested-by: Cindy Lin <xcl@google.com>
1 file changed