The Android NDK is required to build native modules for Android. Download the NDK r19 or newer archive from the following site: Download the Android NDK on developer.android.com To install the Android NDK, simply expand the archive in the folder where you want to install it.
Google removed openssl from Android 7+. You must build openssl libs by yourself.
Edit the mkall script to configure NDK path. Set the NDK to the directory where the NDK is installed.
Run /bin/bash mkall > build.log script. Libraries will be installed to ./target-architecture/lib.
Run /bin/bash packjni to generate jniLibs archive for Android Studio.