[clang] [Clang] Enable -fextend-lifetimes at -Og (PR #118026)

[Mikael Holmén via cfe-commits]

mikaelholmen wrote:

> > I did some downstream testing with "-Og" since this patch and noticed that e.g.
> 
> Thanks for catching these - in terms of legalizer support it looks like everything relevant is implemented except for `SoftenFloatOperand`, so that should be a straightforward fix. The target-specific error is also trivial (`FAKE_USE` has a size of 0), but it would be preferable if every target didn't need to account for it - previously there was a discussion of whether `FAKE_USE` should have `isPosition`, and this probably settles that since it would allow them to be treated correctly by-default.
> 
> I'll revert this for now (after verifying), since it may take a little time to confirm that changing `isPosition()` doesn't introduce any new bugs; I'll try to expand the fake use tests to cover more targets at the same time.

Thanks!

https://github.com/llvm/llvm-project/pull/118026