Rendering on the CPU uses the Embree BVH layout, whether the OptiX denoiser is enabled or not.
This means the "build_bvh" function gets a "BVHEmbree" object to fill and not a "BVHMulti" as it
was assuming before, which caused crashes due to memory geting overwritten incorrectly. This
fixes that by redirecting Embree BVH builds to the Embree device.
Manifest Tasks: T83925