extract_utils: bp_builder: use existing target element if possible

Change-Id: Ia92c66f3200b44ada253d03bf7e6cd4f9100b8d5

Author: luk1337

extract_utils/bp_builder.py

@@ -229,6 +229,8 @@ def target(self, f: File, machine: EM, deps: Optional[List[str]]):
         target_dict: Dict[str, bp_type] = {}
         if 'target' not in self.o:
             self.o['target'] = target_dict
+        else:
+            target_dict = self.o['target']
 
         rel_path = self.__file_rel_sub_path(f.dst)
         if machine == EM.QDSP6: