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

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

Change-Id: Ia0272e51be4ddede1e6bc188dfb892979626a7cd
BUG: 1171524
Signed-off-by: Harshavardhana <harsha@harshavardhana.net>
Reviewed-on: http://review.gluster.org/9252
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Niels de Vos <ndevos@redhat.com>
Reviewed-by: Raghavendra Bhat <raghavendra@redhat.com>
Tested-by: Raghavendra Bhat <raghavendra@redhat.com>