[lld] [lld-macho,BalancedPartition] Simplify relocation hash and avoid xxHash (PR #121729)

[Ellis Hoag via llvm-commits]

https://github.com/ellishg commented:

Only very minor size changes on my end. I'm curious if @Colibrow sees and size regressions. LGTM after fixing the `data.size() < windowSize` issue.

https://github.com/llvm/llvm-project/pull/121729