[clang] [clang-cl][flang][dxc] Fix opts exposed to clang-cl/dxc by mistake (PR #118640)

[Mészáros Gergely via cfe-commits]

Maetveis wrote:

@HaohaiWen can you review and approve if it looks good now for clang-cl? I'll try pinging discord and waiting a little bit for HLSL people before merging.

Gentle ping @bob80905. 

https://github.com/llvm/llvm-project/pull/118640