[clang] [DebugInfo] Init DwarfVersion of MCOptions like the other. (PR #146666)

[Liu Ke via cfe-commits]

Sockke wrote:

> I guess this would be visible when using clang to compile some assembly code and requesting debug info of a specific version

We have pre-built bitcode. When compiling bitcode, we need to request specific debug info version - like Distributed ThinLTO's backend process - to keep version consistency.

https://github.com/llvm/llvm-project/pull/146666