Bug: No usable GPU found, --gpu-layers option will be ignored but AMD GPU does exist

### Contact Details _No response_ ### What happened? Similar to https://github.com/mozilla-ai/llamafile/issues/384 , when I ran: `llamafile.exe --log-disable -m MODEL --mmproj MMPROJ -ngl 9999 --chat` It shows: `warning: no usable GPU found, --gpu-latyers option will be ignored` Yet my box have `AMD Ryzen 5 6650H with Radeon Graphics` which has 8GB shared VRAM. It can play videogames which requries 8GB VRAM just fine, so why llamafile won't use this? --- Other question, will llamafile use NPU too? Because there are lots of mini PCs sold online and those doesn't have big GPU but AI-optimized NPU. ### Version llamafile-0.10.2-alpha ### What operating system are you seeing the problem on? _No response_ ### Relevant log output ```shell ```