tzdata: allow host build

uClibc uses its own format for timezone info. OTOH, we can generate
uClibc-compatible timezone info from existing tzdata.

Add a host-version of tzdata, so we can harvest its installed timezone
info.

Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>