package/libvirt: add libnl optional dependency

libnl is an optional dependency (which is enabled by default) since the
addition of the package in commit
ccfc90e1010e42e6529afae3a5ea8bf7226dabc1

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>

package/libvirt/libvirt.mk

@@ -134,6 +134,13 @@ else
 LIBVIRT_CONF_OPTS += -Dlibiscsi=disabled
 endif
 
+ifeq ($(BR2_PACKAGE_LIBNL),y)
+LIBVIRT_CONF_OPTS += -Dlibnl=enabled
+LIBVIRT_DEPENDENCIES += libnl
+else
+LIBVIRT_CONF_OPTS += -Dlibnl=disabled
+endif
+
 ifeq ($(BR2_PACKAGE_LIBPCAP),y)
 LIBVIRT_CONF_OPTS += -Dlibpcap=enabled
 LIBVIRT_DEPENDENCIES += libpcap