Separating Android.mk file for each flavor

I’m using Android Studio and Gradle.

There are some flavors that having a little differrent views and features.

So, for each flavor, I want to switch Android.mk file.

ex)
flavorA -> Android_flavorA.mk
flavorB -> Android_flavorB.mk

but, in externalNativeBuild and ndkBuild block, couldn’t dynamically change a path of Android.mk.

Anybody know about this?