pkg-autotools: fix bad GETTEXTIZE_OPT assignment

HOST_PKG_GETTEXTIZE_OPT should get assigned PKG_GETTEXTIZE_OPT and not
PKG_GETTEXTIZE. Fixes:
http://autobuild.buildroot.net/results/087/087e860173069f58fa9ceb2460d7455d31b2dff8/



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