This comes from #541. We let it as is in case it helps building on Mac.

diff --git a/setupext.py b/setupext.py
--- a/setupext.py
+++ b/setupext.py
@@ -665,6 +665,7 @@ class BackendMacOSX(OptionalPackage):
     name = 'macosx'
 
     def check(self):
+        raise Skipped("MacOSX backend disabled")
         if sys.platform != 'darwin':
             raise Skipped("Mac OS-X only")
         return super().check()
-- 
2.20.1