Gradle 4.0 came out yesterday and I updated my project for it.
Now I am getting the following warning:
Gradle now uses separate output directories
This is due to the change introduced in Gradle 4.0: it now uses separate output directories if there are multiple language sources.
To return to the old behaviour and get rid of the warning, insert this into your build.gradle:
// Change the output directory for the main source set back to the old path
sourceSets.main.output.classesDir = new File(buildDir, "classes/main")
Reference: https://docs.gradle.org/4.0/release-notes.html#multiple-class-directories-for-a-single-source-set