Draft: wait-for-stop integration into onionmasq

This doesn't work yet.

I'm testing with the following setup:

./build-ndk.sh # cross-compiling
cd ./android/OnionmasqAndroid
./gradlew build # builds the aar 

build and install the app, .e.g.

./gradlew assembleDebug
adb install -t sampleapp/build/outputs/apk/debug/sampleapp-debug.apk