[lld] [lld-macho] Handle InputSection targets in branch range extension logic (PR #126347)

[via llvm-commits]

alx32 wrote:

While trying to get a Rust repro for this - it turns out that I was misdiagnosing the root issue. 

The issue comes from `--icf=safe_thunks` creating branches with `InputSection` targets, the input files don't actually have branches with `InputSection` targets natively. 

While this PR still fixes the issue - it seems like fixing the root cause would be better: https://github.com/llvm/llvm-project/pull/126835

I'll close PR after landing the alternate one above. 

https://github.com/llvm/llvm-project/pull/126347