Hard links are not handled by nar, so installing from binary cache
unnecessarily duplicates data. Also, it's more common to use symlinks for the
tzdata package in other distributions.
We're already using tzcode inside tzdata, so let's make it available as
an output here. The reason we need it is in order to compile OpenCFLite.
Signed-off-by: aszlig <aszlig@redmoonstudios.org>
