After I add the extern object, how do I modify the utils tool so that it still works?

I introduced an extern function in my p4 program, in order to verify the usage of extern. However, I found that when I introduced extern and used utils again to create a mininet network and started it with the make run command, the virtual network could not be started and the terminal gave the following error:

As you can see, I modified the Makefile file in the utils folder as the example given by bmv2 in git, and added the command to compile the cpp program in it, but I didn’t find the setting related to simple_switch. Reading the Makefile file I learned that the tool creates the network and p4 switch through the file, but I still haven’t figured out how to modify it so that it can load external programs for me.
I understand that you can add external programs using --extern-modules in simple_switch, but I don’t know how to add it to the utils tool.