enter_chroot: Add a flag to specify the working directory in chroot.

Flag `--working_dir <path>` specifies enter_chroot.sh to run the
command in /mnt/host/source/<path>.  In interactive mode, this flag
specifies the default working directory of the shell.

TEST=manually test

Change-Id: I36a2eca9fbc2b38c5192a5e04ccde47dfe5830c2
Reviewed-on: https://chromium-review.googlesource.com/903665
Commit-Ready: Yong Hong <yhong@google.com>
Tested-by: Yong Hong <yhong@google.com>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
1 file changed