factory_install: Allow debug console if cros_debug is defined.

When installation failed, we do want a friendly environment to help debugging.
Since kernel is always signed, a cros_debug ensures that the system was not boot
as official signed images.

To enable the flag:
 - netboot: Override command line by files on TFTP.
 - factory install shim: Add cros_debug into --boot_args.

BUG=none
TEST=build_image factory_install --boot_args "noinitrd cros_debug"

Change-Id: I6e24c8a2ceda8d696be66ff212b45c5ab697fb3f
Reviewed-on: https://chromium-review.googlesource.com/249006
Reviewed-by: Ricky Liang <jcliang@chromium.org>
Tested-by: Hung-Te Lin <hungte@chromium.org>
Reviewed-by: Wei-Ning Huang <wnhuang@chromium.org>
Commit-Queue: Hung-Te Lin <hungte@chromium.org>
1 file changed