package/libevas-generic-loaders: needs zlib

Fixes:
http://autobuild.buildroot.net/results/5d4/5d41cec63a15dc5f31460c8cecd6054119ddb1fc/build-end.log



Signed-off-by: Romain Naour <romain.naour@openwide.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>