[llvm] [MemoryBuiltins] Consider index type size when aggregating gep offsets (PR #132365)

[via llvm-commits]

https://github.com/serge-sans-paille commented:

I thought there would be test cases where the offset accumulation would lead to an overflow. What should we do in that case?

https://github.com/llvm/llvm-project/pull/132365