java.util.Arrays.copyOf(...), that is available only on Android API level 9 and above. This means that your Android app might not work with Froyo devices if you build it with Scala 2.11. Because the current market share of the API level < 9 is less than 1 percent, this limitation is not serious.
However, if you stick to support older Android devices, here is a workaround:
-dontwarn scala.collection.mutable.**in your proguard settings.
- Do not use
mutable.AnyRefMap. Make sure these classes not be called in transitive way.