[llvm] [AVR] Emit relocation record for local branch (PR #145291)

[Patryk Wychowaniec via llvm-commits]

Patryk27 wrote:

Bumping so that this merge request doesn't go stale - I'd be up for merging this.

Emitting relocations is what GCC does as well, and even LLVM does it for some (if not most?) targets, cf. RISC-V (at least last time I checked).

This also makes the code less hacky, since now that I think about it, the entire `If the jump is too large to encode it, fall back to a relocation.` was kinda awkward 😅 

https://github.com/llvm/llvm-project/pull/145291