[clang] [clang] Don't use `VarDecl` of local variables as `ManglingContextDecl` for lambdas (PR #179035)

[Jan Kokemüller via cfe-commits]

jiixyj wrote:

Alright, I think I ended up with something that is closer to the original spirit of the code and a little bit easier to reason about. I updated the PR description. What do you think?

https://github.com/llvm/llvm-project/pull/179035