Synchronize localtime between Chrome OS and host OS:

Instead of manually setting a timezone in the host OS, link up the localtime information, so that timezone modification in Chrome OS is instantly updated in the host OS.

We bindmount /var/lib/timezone in enter-chroot. During installation, we link /etc/localtime to /var/lib/timezone/localtime.
Note that /var/lib/timezone/localtime is itself a symbolic link to a file in /usr/share/zoneinfo, but it should work as long as the zoneinfo information is the same in Chrome OS and the host OS (I see no reason why they should be different).