Dex Transformation not getting generated for build variants after migrating from Gradle 2.14/AGP 2.2 to Gradle 5.x/AGP 3.5

Question

I'm working on upgrading Android Gradle Plugin from 2.2.0 to 3.5 (Gradle 2.14 --> 5.x). While doing so, I observe that dex transformations which were earlier generated for our build variants( we have 6 flavours) are not getting generated now. I verified by printing the below code in both the build.gradle files (2.14 & 5.x)

android.applicationVariants.all { variant ->
    println "Just project variants = ${project.tasks}"
}