[llvm] [DirectX backend] emits metadata for DXIL version. (PR #88350)

[Xiang Li via llvm-commits]

python3kgae wrote:

> > Default to DXIL 1.0
> 
> Can you clarify what the intent of this PR is please? It looks like it is actually trying to match current DXC behavior that assumes that the DXIL version is tied to the SM version?

The intent for this PR is to match current DXC behavior when DXIL version is not set separately.
Once we have DXIL version sent to backend with Triple or something else, we could use that in another PR.

https://github.com/llvm/llvm-project/pull/88350