[clang] [CIR] Upstream emitAndUpdateRetAlloca (PR #129933)

[David Olsen via cfe-commits]

dkolsen-pgi wrote:

I have mixed feelings about this change.  It mostly overlaps with what I am working on, which is class `LexicalScope`, which has a bunch of the code for handling the return value.  I think I would prefer that this PR be dropped, as the changes will be part of the PR I am working on.


https://github.com/llvm/llvm-project/pull/129933