[clang] [clang][SYCL] Emit non-exported device symbols with internal/linkonce_odr linkage (PR #215437)

[Yury Plyakhin via cfe-commits]

YuriPlyakhin wrote:

> overall the change is fine with me but i agree it would be better if we could just do LTO, i worked on SYCL LTO support a bit in the downstream compiler but put it on hold as it would be specific to the old offload model, since we have much less baggage upstream it would be nice to see if we could enable LTO sooner rather than later

yep, LTO is the next on my list, after no-rdc.

https://github.com/llvm/llvm-project/pull/215437