Update bb.org_4gb_stable.sh
Update bb.org_4gb_stable.sh

Temporarily try to build xM and X15 images.
beagleboard/image-builder,beagleboard/image-builder,jadonk/image-builder,miloh/image-builder,robert-budde/omap-image-builder,RobertCNelson/omap-image-builder,robert-budde/omap-image-builder,jadonk/image-builder,RobertCNelson/omap-image-builder,miloh/image-builder