[llvm] [DwarfGenerator] Calculate relative offset according to Dwarf Version (PR #84847)

[Will Hawkins via llvm-commits]

hawkinsw wrote:

> Go ahead and click "Squash and merge" when you're ready. Only thing to make sure is that you haven't got your email address hidden by GitHub. Then keep an eye out for failure emails from the build bots (not all failures will necessarily be anything to do with your change though).

Thanks! I have done a few with libc++ so here. we. go.

https://github.com/llvm/llvm-project/pull/84847