spdx: Add set helper for list properties

This adds the set helper for list properties to allow list members to be
replaced with a new list. This is necessary as it is (currently) the
only way to replace the default value for a list member.

(From OE-Core rev: 8280b857c510646cd10167dd2ea9a0c2d5f1e800)

Signed-off-by: Joshua Watt <JPEWhacker@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/lib/oe/spdx.py

@@ -105,10 +105,13 @@ class _ListProperty(_Property):
                 obj._spdx[name] = []
             return obj._spdx[name]
 
+        def set_helper(obj, value):
+            obj._spdx[name] = list(value)
+
         def del_helper(obj):
             del obj._spdx[name]
 
-        attrs[name] = property(get_helper, None, del_helper)
+        attrs[name] = property(get_helper, set_helper, del_helper)
 
     def init(self, source):
         return [self.prop.init(o) for o in source]