Does the A770 use the Xe driver? If so then it might work with the scripts that I've been using to build llama.cpp with SYCL support for the Arc Pro B70.

https://github.com/cptskippy/battlemage-llm-gateway

It's designed so that you can re-run the scripts to pull the latest updates. When Muse Glimmer was released the other day I just ran the 02 script to build the latest version of llama.cpp with support for it.