[clang] [Clang]fix dependent qualified base member lookup crash (PR #199403)

[via cfe-commits]

Serosh-commits wrote:

> > ... for a record that has no definition ...
> 
> Could you please elaborate? I don't find a record having no definition in the crash reproducer.

so as per i think  in the reproducer itself when we hit `X<int>::S` we are  in the middle of instantiating `X<int>` so then its definition isn't complete yet  so that's  whyy `BaseRecord->hasDefinition()` is false at that exact point even though both records look fine in the final AST

https://github.com/llvm/llvm-project/pull/199403