[Bug 58580] macOS clang: -msabi=ms unrecognized option... causes x86_64-unix/*.a files to be missing. winegcc cannot link against libadvapi32 et al

[WineHQ Bugzilla]

http://bugs.winehq.org/show_bug.cgi?id=58580

--- Comment #2 from Alexandre Julliard  ---
Building with Unix clang on x86-64 is not supported, because without -mabi=ms
the ABIs are not compatible. It will work for simple things but it will break
eventually, for instance when using varargs functions.

On macOS there is now the further problem that we need to switch the %gs
register between PE and Unix code, which means that Winelib dlls can't be
supported anymore. You'll need to use the new Unix call interface.