[llvm] [DWARFLinkerParallel] Add support for -odr mode. (PR #68721)

[via llvm-commits]

avl-llvm wrote:

> > DWARFLinker would still need to be deterministic, even on old/bad/different input
> 
> +1
> 
> > though maybe Apple & other folks would be open to it having an error on "bad" input rather than having to figure out a way to have a deterministic successful output.
> 
> As long as the input DWARF is valid, we need to be able to link it. Maybe a slow path would be okay if we can guarantee our toolchain doesn't trigger it (i.e. clang & Swift).

yes, more slower but deterministic handling is in my future plans. And we can use slower version with unknown sources and faster version with DWARF generated by clang&Swift (if inconsistent cases would be resolved). 

https://github.com/llvm/llvm-project/pull/68721