I discovered the --verbose flag, when I ran the plugin add command with it, the log showed each command as it was executed, turned out gradle.bat and gradlew in ~/git/ionic/myApp/platforms/android weren't executable, when I did a chmod a+x gradle*** in that directory the **cordova plugin add worked. Hope that helps
EDIT: I just realized that I posted in the wrong topic, sorry for the mistake, I'm new here