Support AdaptiveCPP

[VaiTon]

Feature Description

AdaptiveCpp is an open source SYCL compiler able to compile SYCL code to bytecode that gets then JIT-compiled on first run, enabling the use of the same binary in different contexts (OpenMP on CPU, SPIRV, CUDA or HIP).

Motivation

The Single Pass Compiler provided by AdaptiveCpp is able to JIT compile to different platforms, using different backends. In the long run it could be one of the best alternatives to CUDA for heterogeneous programming.

Possible Implementation

ggml supports SYCL, but uses a lot of DPC++ specific constructs. They should be abstracted away / removed to adhere to the SYCL standard.

[tuaris]

I was going to start a new discussion, but (thankfully) I found this existing one. I'd also like to express support for this. Would also like to add that AdaptiveCpp was previously known as hipSYCL or Open SYCL.

This is mostly for the purpose of getting llama.cpp working on FreeBSD using a SYCL backend since AdaptiveCpp is readily available on that platform.