Signed-off-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

Upstream antirez/ds4 splits the SSD expert-cache into its own ds4_ssd.c
translation unit, whose symbols (ds4_ssd_memory_lock_acquire/release,
ds4_ssd_cache_experts_for_byte_budget, ds4_ssd_auto_cache_plan) are
referenced by ds4.c/ds4_cpu.o. The dependency-bump automation regenerated
this branch from clean master and dropped the prior linkage fix, so the
cpu-ds4 / cublas-ds4 backend builds fail again with undefined references.

Re-apply the ds4_ssd.o linkage GPU-agnostically (mirroring ds4_distributed.o)
in both the backend Makefile (DS4_OBJ_TARGET + the engine-object build rule
for every GPU mode) and CMakeLists.txt (list(APPEND DS4_OBJS ds4_ssd.o)).

Signed-off-by: Ettore Di Giacinto <mudler@localai.io>
Assisted-by: Claude:opus-4.8 [Claude Code]