build: FreeBSD 11-Current causes libtool to fail with '-shared'

Thanks for Markiyan Kushnir <markiyan.kushnir@gmail.com> for
reporting this

Change-Id: I7f637295c7c2d54c33a4c16e29daf0b518874911
BUG: 1111774
Signed-off-by: Harshavardhana <harsha@harshavardhana.net>
Reviewed-on: http://review.gluster.org/9251
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Niels de Vos <ndevos@redhat.com>