[clang] [APINotes] Apply APINotes to non-global decls in a LinkageSpecDecl (PR #176792)

[Saleem Abdulrasool via cfe-commits]

https://github.com/compnerd commented:

Do we need to consider something like:

```c++
namespace {
extern "C++" {
struct S {
  extern "C" static void f();
};
}
}
```

`::S::f` is actually exported as `f` in the global namespace here I believe.

https://github.com/llvm/llvm-project/pull/176792