[llvm] [Attributor] Report change when updating ReachesReturn (PR #108965)

[Johannes Doerfert via llvm-commits]

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

This is a correctness problem and the fix looks good, except style.

Please commit asap with style changes and add the reproducer later.

https://github.com/llvm/llvm-project/pull/108965