Pin upstream llama.cpp b9645 and build it against the nixpkgs-latest
input (the flake's pinned nixpkgs only carries the pre-tools/ui b8983).
ROCm deps come from rocmPackages.gfx1151, so clr/rocBLAS/hipBLAS are
built for gfx1151 only; clr's own build is arch-independent, so its
store path stays substitutable. Vulkan on, CPU variants with znver5 /
AVX-512, web UI and npm toolchain dropped.
Ported from nixos-config's llm-engine.nix with two fixes: npmConfigHook
hard-fails when npmDeps is null, so nodejs and the hook are stripped
from nativeBuildInputs, and CMAKE_HIP_FLAGS is appended to
cmakeFlagsArray because the cmake hook word-splits plain cmakeFlags.
Verified on the Radeon 8060S (gfx1151): llama-bench loads both ROCm and
Vulkan backends and completes pp16/tg8 runs.
Alexander Miroshnichenko
73f782d523