Draft: OpenCL and Intel Vulkan Raytracing

Add OpenCL + Mesa's new Gallium frontend 'RustICL' + Intel Vulkan Raytracing + enabled intel_hasvk for older integrated Intel GPU Vulkan support.

I've moved llvm to pkgs/llvm/base.bst due to splitting out the sources to pkgs/llvm/src.yml as it needs to be shared with pkgs/llvm/libclc.bst (this is similar to how the freedesktop-sdk has arranged things so that it can build libclc).

RustICL is the new OpenCL state tracker that comes with Mesa3D, which boasts the ability to run OpenCL on top of Vulkan via Zink, which could make things interesting for a unified compute stack. I needed to add bindgen-cli for this.

For Intel DG2 (ARC) hardware to function properly we will most likely need to wait for Linux Kernel 6.2 and the latest firmware, but this should be fine to merge before that.

Intel has recently split their Haswell and older Vulkan driver into intel_hasvk, this makes sure it is included.

Keeping this as draft as I do some testing here on real hardware.