Fix tzdata update tools for 'backzone'.

To maintain the status quo, we need to pull in backzone file. This file
can't be built on its own, so the easiest fix is to give zic(1) all the
files at once.

We also now have a situation where we have links to links, so we need to
dereference them until we find actual data.

Bug: 18330681
Change-Id: I03f4aa8e6e23802dc35cbff2f74f325eb17d7b2b
Merge "Fix tzdata update tools for 'backzone'."