Spitz AX / GL-X3000 OpenWRT SDK


I was going through sdk, the OpenWRT SDK github page. I have downloaded the repo and trying the download.sh script. It does not show support for my device, Spitz AX / GL-X3000. How can I build custom applications for my device, Spitz AX / GL-X3000?

Please help me with a SDK for OpenWRT for my device Spitz AX / GL-X3000.
I appreciate any help, thanks!