OSX: Fix T37602, quitting from the File Menu does not ask

Referenced by issue #37602, Ask To Save - OSX, Linux

release/scripts/startup/bl_ui/space_info.py

@@ -83,6 +83,7 @@ class INFO_MT_file(Menu):
     bl_label = "File"
 
     def draw(self, context):
+        import sys
         layout = self.layout
 
         layout.operator_context = 'INVOKE_AREA'
@@ -131,6 +132,8 @@ class INFO_MT_file(Menu):
         layout.separator()
 
         layout.operator_context = 'EXEC_AREA'
+        if sys.platform == "darwin":
+            layout.operator_context = 'INVOKE_SCREEN' # quit dialog
         layout.operator("wm.quit_blender", text="Quit", icon='QUIT')