ERROR: android-support-v4.jar" already exists!`

When there is a plugin already installed that uses `android-support-v4.jar` and one tries to install "https://github.com/MobileChromeApps/cordova-plugin-android-support-v4", cordova fails with error `android-support-v4.jar" already exists!` (when trying to copy the library with `<source-file src="android-support-v4.jar" target-dir="libs" />` instruction).

How to reproduce: 
1. Install com.admob.google plugin from https://github.com/appfeel/admob-google-cordova
2. Install android.support.v4 plugin:

```
cordova plugin add com.admob.google
cordova plugin add https://github.com/MobileChromeApps/cordova-plugin-android-support-v4
```