update_packages_and_run_tests: add chroot args

This allows us to specify a custom chroot to run commands in. This
allows for isolated runs, and easier gardening.

BUG=b:325884106, b:325895866
TEST=./test_update_llvm_next_google3_cq_recipes.sh on chrotomation

Change-Id: I1681f7a96be758dd332f30dd0ec4ca8052705c1f
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/toolchain-utils/+/5362313
Tested-by: George Burgess <gbiv@chromium.org>
Commit-Queue: George Burgess <gbiv@chromium.org>
Reviewed-by: Jordan Abrahams-Whitehead <ajordanr@google.com>
7 files changed