This patch backports https://github.com/llvm/llvm-project/pull/77016 into the DWARFLinkerParallel.
This patch creates DWARFLinkerBase library, places DWARFLinker code into DWARFLinker\Classic, places DWARFLinkerParallel into DWARFLinker\Parallel. updates BOLT to use new library. This patch is NFC.