build: explicitly delay adding of object files to linking

Before, `do_the_symbol_stuff` would implicitly come before
`handle_add_object`, which adds object files to the linking task.

With newer (2.0.x) versions of waf, the ordering seems to get more
optimized, and thus we have to declare that the function that creates
the linking task should come before the task that adds object files
to the task.

waftools/generators/sources.py

@@ -94,6 +94,7 @@ def __wayland_protocol_header__(ctx, **kwargs):
 @TaskGen.feature('cshlib')
 @TaskGen.feature('cstlib')
 @TaskGen.feature('apply_link')
+@TaskGen.after_method('do_the_symbol_stuff')
 def handle_add_object(tgen):
     if getattr(tgen, 'add_object', None):
         for input in Utils.to_list(tgen.add_object):