[clang] [Clang] Use ConstantExpr::getGetElementPtr() with DataLayout (PR #225415)

[Andrzej Warzyński via cfe-commits]

banach-space wrote:

This change has caused ClangIR regressions:
* https://lab.llvm.org/buildbot/#/builders/242/builds/157

There should be an automated notification sent to this PR, I'm not sure why that didn't happen (we are investigating).

@nikic , would you be able to take a look at the failures? Thank you!

https://github.com/llvm/llvm-project/pull/225415