[clang] [clang] Generate nuw GEPs for struct member accesses (PR #99538)

[John McCall via cfe-commits]

rjmccall wrote:

`CGBuilder` is just aiming to provide an `Address` overload of LLVM's `CreateStructGEP`.  It seems wrong for two overloads to have subtly different behavior.

Is there a reason why LLVM's `CreateStructGEP` doesn't add `nuw` itself?

https://github.com/llvm/llvm-project/pull/99538