How to remove unused resources from libraries?

Question

At first I know Remove all unused resources from an android project, but that is only for projects.

I want to remove unused images from a li

Answer 1

I almost missed it to write that there is now a nice solution:

android {
    buildTypes {
        release {
            minifyEnabled true
            shrinkResources true
        }
    }
}

This was annouced on Google+ by Tor Norbye for the build tools version 0.14.0