make_factory_toolkit: Use the new pack function in installer

The installer supports packing factory toolkit now. Let's use it instead
of packing here.

Also, add a timestamp and builder info to ID string when version is not
specified.

BUG=chrome-os-partner:25941
TEST=Unpack, modify a file, and then repack.
TEST=Build without version. Check ID string.
CQ-DEPEND=CL:186946

Change-Id: Ie8b513e49899e8b4470c855a4bf4e359c104049b
Signed-off-by: Vic (Chun-Ju) Yang <victoryang@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/186954
Reviewed-by: Jon Salz <jsalz@chromium.org>
1 file changed