[llvm] [DirectX] Set Shader Flag DisableOptimizations. (PR #123136)

[S. Bharadwaj Yadavalli via llvm-commits]

bharadwajy wrote:

Since `optnone` function atribute is not set when `-O0` (or `-Od`) is specified, my experiements to set them appear to reveal that such a change interferes adversely with the exisiting DXIL linkage assumptions / rules. To prevent "non-standard" DXIL metadata (i.e., that not specified in DXIL Spec) from being generated in the final DXIL output, I pushed changes to delete the metadata once its intent is captured in Metadata analysis pass. Following the discussion offline, @bogner, please see if this would address the concerns raised. Thanks!

https://github.com/llvm/llvm-project/pull/123136