[clang] [clang][DebugInfo] Attach `DISubprogram` to additional call variants (PR #166202)

[J. Ryan Stinnett via cfe-commits]

https://github.com/jryans commented:

Thanks for the review! :smile: 

> Does -g[no-]omit-unreferenced-methods still work as expected?

Yes, that appears to be covered by at least the `clang/test/DebugInfo/CXX/incomplete-types.cpp` test. Switching the omit flag on does the expected thing of limiting emitted function types.

https://github.com/llvm/llvm-project/pull/166202