[llvm] TargetLibraryInfo: Use pointer index size to determine getSizeTSize(). (PR #118747)

[Owen Anderson via llvm-commits]

resistor wrote:

> This LGTM conceptually, but I think you do need to also switch calls in SLC to use getSizeTSize in places that currently use getIntPtrType. These values previously happened to be the same, but they won't be now (if the pointer and index size differ) and that will lead to assertion failures.

I threaded it through SLC, PTAL

https://github.com/llvm/llvm-project/pull/118747