[clang] [llvm] [AVR] Fix Avr indvar detection and strength reduction (missed optimization) (PR #152028)

[Patryk Wychowaniec via llvm-commits]

Patryk27 wrote:

> Rust normally uses a patched llvm and I am directly using this PR so that could be the cause but I want to check that first. 

Yeah, I usually just cherry-pick my changes on top of Rust's fork of LLVM, to make sure I don't bring too many unrelated changes there 👀 

https://github.com/llvm/llvm-project/pull/152028