I'm unsure whether the latest OSX UI changes have been merged or not, but what I did yesterday was to set up my build system on my other Mac (not my work computer) and "start from scratch". The following are my findings on what was needed:
1) Search this mail archive for Nicolas' post with CAPSImage.framework v5 - and don't forget the caps.diff posted later which adds types to CommonTypes.h
2) I couldn't find any pre-built fat binaries for SDL2 (i386+x64) so I set up a build environment to do that. The supplied instructions by the SDL project did not work for me but after some patching I can now build a fat SDL2 .dylib (v2.0.4)
3) Use Macports to install +universal (fat) versions of libpng and libportaudio2
4) Strangely enough cmake -G Xcode doesn't not like neither my readline nor portaudio - a quick check indicates that the files are found but the extra check to see if they contain specific methods fail. I don't know whether this is something that's changed in the current source compared to last time I built Hatari, or whether it's due to me starting fresh on a new computer. Not solved.
5) The recent changes to gui-osx seem to require Xcode 7 ("SDLMain.xib: error: The document "(null)" requires Xcode 7.0 or later") and Xcode 7 requires the latest OSX so at this point I had to update both my OS and Xcode ....
... but after all that I now have a new binary built. There does seem to be some UI issues (text at FPU selection) and I would very much like it if others can test this binary. Compared to my previous builds it's done on a new version of the OS, new Xcode, I use a self-built fat SDL2 .dylib instead of the distributed Framework etc etc.
(Yes, I did all this to make sure I was ready when there's a decision to release Hatari v2.0 - my work computer requires a fresh install so I really needed to get this up and running on another computer)