Hello Moh Zahra,
The problem in this case is that there is no core-image-weston recipe available. This issue has been reported but there is no information yet on a possible fix.
If you wish to build a Weston image you should be able to use Wayland as backend on the local.conf file and then build a compatible image. This is supported on the BSP release, I’ll check if it’s available also on the Yocto Community BSP (the Krogoth branch in particular).
Regards,