The task is simple, you have to write a ANE that has one method named execute(str:String):boolean
what this method does is that it runs a shell command using the string as parameter, and returns true when the command has run.
If you can add an event to receive what the commands reply, that would be a nice extra and will be considered.
Running a shell command is easy in the java side:
Process su = Runtime.getRuntime().exec("su"); //this runs su in the shell