Comment 2 for bug 8088

I think I'd err towards using UTC without asking if Ubuntu is the only operating
system on the disk, and asking otherwise (you might well have another GNU/Linux
installation that you've configured to use local time). This doesn't necessarily
have to conflict with Matt's comments about defaults.

We'll need to make something in d-i figure this out from os-prober (probably in
prebaseconfig, before unmounting the installed system; the various bootloader
installers already run os-prober, but I'd rather not modify each of them one by
one), stash it in debconf, and fish it out again in base-config.