build_packages: Add internal flag

Add the internal flag as a convenience option for doing an internal
build.

BUG=None
TEST=manual

Change-Id: I2c95a53a56cc26d8af1d285210d6f28c49023b5b
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosutils/+/2173298
Tested-by: Alex Klein <saklein@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
Reviewed-by: Chris McDonald <cjmcdonald@chromium.org>
Commit-Queue: Alex Klein <saklein@chromium.org>
1 file changed