[clang] [clang][DebugInfo] Make fwd decl call site debug info consistent for methods (PR #222263)

[Orlando Cazalet-Hyams via cfe-commits]

OCHyams wrote:

> Maybe you meant to request reviews instead of setting assignments…? 🤔

I did indeed, oops

> This makes sense to me; please add a comment as to why there are two paths for DISubprogram production in the code added though.

Will do

> Would it make sense to push this logic into EmitFunctionDecl, or is that too complicated?

I can have a look

https://github.com/llvm/llvm-project/pull/222263