[llvm] [ASan] Prevent assert from scalable vectors in FunctionStackPoisoner. (PR #155357)

[David Green via llvm-commits]

davemgreen wrote:

This came up again in #155505. That tries to go the isInterestingAlloca route, but is failing some tests because of it. I will push this to get it fixed if htat is OK and if we need to adjust it we always can.

https://github.com/llvm/llvm-project/pull/155357