[clang] [compiler-rt] [llvm] [TargetLowering] Set the default `getCmpLibcallReturnType` to word size (PR #192441)

[Alexander Richardson via cfe-commits]

https://github.com/arichardson approved this pull request.

LGTM but it would probably be good to get this signed off by the target maintainers where the codegen has changed. 

https://github.com/llvm/llvm-project/pull/192441