[clang] [Clang][SYCL] Introduce clang-sycl-link-wrapper to link SYCL offloading device code (Part 1 of many) (PR #112245)

[Joseph Huber via cfe-commits]

jhuber6 wrote:

> I think we could all benefit from some documentation describing how the SYCL compiler flow is intended to work, what tools are added/modified, and what the expected outputs are at each compiler phase. Without some idea of the architecture of what is being built changes like this and #110771 don't make sense and are really difficult to review.
> 
> This isn't like introducing a new backend or something where we have a defined and understood architecture to evaluate against. We're getting patches that only represent small parts of the whole without any context to understand how it will all come together in the end.
> 
> What worries me is that from the parts I see, it doesn't align with any of the community design principles.

>From what I understand, they want to integrate SYCL linking into the existing linker wrapper framework. That tool basically extracts embedded offload binaries and then calls `clang --target=${target} extracted.o -o image` and then embeds that into the runtime. They wanted to know how to do that so my suggestion was to make something that looked like a linker so that control flow worked. I'm not familiar with the other serialization format however.

https://github.com/llvm/llvm-project/pull/112245