[llvm] Add -Wms-bitfield-padding warning when possible (PR #139828)

[Vlad Serebrennikov via llvm-commits]

Endilll wrote:

> > > @mstorsjo @Endilll @IanWood1 given you're doing stage2+ builds would you folk mind seeing if this warning triggers for you? after applying #139825 if possible
> > 
> > 
> > I applied changes from both PRs, and I'm seeing the following warnings (heavily deduplicated):
> 
> Thank you very much! I'll try to add the fixes for those ones.
> 
> What targets do you have enabled?

Only X86

https://github.com/llvm/llvm-project/pull/139828