[clang] [llvm] [BOLT] Add --ba flag to deprecate --nl (PR #164257)

[Paschalis Mpeis via llvm-commits]

paschalis-mpeis wrote:

Thanks Amir. I've provided a callback instead for the warning, similar to `RT_HFSORT_PLUS`.

I'll merge in a day or two if there are no further comments.

https://github.com/llvm/llvm-project/pull/164257