osx: Enable qemu feature build on Darwin

Change-Id: Ie5d437aa6c52c180fd8d54680c5f882e75c0bf7e
BUG: 1089172
Signed-off-by: Harshavardhana <harsha@harshavardhana.net>
Reviewed-on: http://review.gluster.org/8448
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Kaleb KEITHLEY <kkeithle@redhat.com>