[llvm] [SDAG] Avoid crash when creating debug fragements for scalable vectors (PR #165233)

[Sander de Smalen via llvm-commits]

sdesmalen-arm wrote:

Clang no longer generates LLVM IR using wide vector types, but rather represents each tuple as individual arguments that are combined together using `insertvalue`s. This means recent versions of Clang no longer have this issue. If this is about a downstream version of Clang then the better solution would be to work around the issue downstream rather than introducing this workaround here in SelectionDAG. We shouldn't be relying on LLVM being able to handle illegal types in the ABI.

https://github.com/llvm/llvm-project/pull/165233