[tz] tzselect from current local time

[Robert Elz]

The problem with that approach is that it assumes that the
system's UTC time is (approximately) correct already.

While testing the implementation, that's almost always going
to be true, and it would work for the cases where either the
user is connecting to a remote system and wants to set their
personal TZ to have times reflect their location, rather than
the system's, and where a user with a laptop just got off the
plane, and wants to set up their system to show local time
for their current location.

But I'd have thought those are relatively less frequent uses
of tzselect - the more common usage would seem to be when
installing a system, where nothing can be assumed about the
system's clock at all, but local time (approximately) is
known - in that case what usually happens is for the user
to choose their timezone, then tell the system what the local
time is, and for UTC to be deduced from that.   Later, when
the system is installed and running, NTP, or something equivalent
can be used to refine the UTC setting, if it was roughly
correct already.

So I'd suggest (if this method is to be retained) that it come
with a warning that it only be used if the system's UTC clock
is already correctly set, which I do not know of any way to
verify that can be expected to work during system installation
(no network yet operating).

kre