userland assembly: build empty.S and fail.S to toplevel and run fail.S with path_properties exit_status

They were just duplicating stuff needlessly while we don't support non-native in-tree builds,
which leads to executable conflicts for C file anyways.

path_properties.py

@@ -320,8 +320,7 @@ path_properties_tuples = (
                                 'freestanding': freestanding_properties,
                             }
                         ),
-                        'empty.S': {'no_build': True},
-                        'fail.S': {'no_build': True},
+                        'fail.S': {'exit_status': 1},
                         'main.c': {
                             'extra_objs_userland_asm': False,
                             'no_executable': True