package/zic: install header

The incoming host-tzdump package requires the tzfile header,
so we isntall it.

[Thomas: remove mkdir -p, unneeded because of the use of install -D,
and change install to $(INSTALL), like we do in all other packages.]

Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
[yann.morin.1998@free.fr: split zic header-install to its own cset]
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>