hostapd: fix static linking

A rebase of Samuel Martin's http://patchwork.ozlabs.org/patch/312320/


hostapd doesn't use pkg-config and upstream likely wouldn't take a patch
to do so (hostapd/wpa_supplicant are used in android builds, and it
doesn't use any auto* stuff either) so pass it in LIBS since we
always build openssl with libz support.

Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>