We already include waf in our source.
Just do git submodule update --init --recursive from /home/ujjval/ardupilot/ and it should be good !
The error is saying you that the ardupilotmega.xml file is missing. This file belong to mavlink submodule and contains mavlink protocol definitions for ardupilot, it is translated from xml to C language at compile time !
but when I clone ardupilot the directory it is not cloning the sub directoty in modules. Then I tried cloning them saperately but then the other sub-directory were not cloned.!! I don’t get why?