[clang] [llvm] [DXIL] Set DXIL Version in DXIL target triple based on shader model version (PR #91407)

[Justin Bogner via cfe-commits]

bogner wrote:

> > It would be nice to mention in the description what the sanitizer fix was compared to the original PR.
> 
> Thanks! The fix to address ASAN failure is in commit [8522e36](https://github.com/llvm/llvm-project/commit/8522e3609869d72b7b457a4752149a802be4662d) of this PR. Updated the description as well.

Since we squash commits when we merge it doesn't really make sense to refer to the hash of the PR in the description - this won't point at anything meaningful once the change is merged and the PR commits get garbage collected.

https://github.com/llvm/llvm-project/pull/91407