[llvm] MachineBlockPlacement: Add tolerance to comparisons (PR #67197)

[via llvm-commits]

spupyrev wrote:

I wonder why the existing implementation of block placement relies on block frequencies (that are relative to the entry block) instead of block counts? Would using counts be equivalent (or very similar) to the rounding suggested in the diff?

https://github.com/llvm/llvm-project/pull/67197