build: Store the jenkins build number in misc_info

If the jenkins build number is available, list it as build_number in
the misc_info.txt file.

Change-Id: I6500c6b53661f2904dff738d25d8a8d24a7dca80
(cherry picked from commit b8e85ff95b19e4cf5e48b411f094bffe0227199e)