[llvm] [DebugInfo] Emit negative DW_AT_bit_offset in explicit signed form (PR #87994)

[David Blaikie via llvm-commits]

https://github.com/dwblaikie approved this pull request.

*shrug* I'm still confused why we emit negative values here & not sure how much to support DWARFv3 these days... , but if it's consistent with GCC & doesn't seem too invasive, I can't fault it too much.

https://github.com/llvm/llvm-project/pull/87994