Firstly, you should make sure that all submodules are cloned.
git submodule init
git submodule update
This project patches swaggerApi submodule, so to untrack changes there execute
echo "AUTOBUILD" >> ./.git/modules/swaggerApi/info/exclude
cd swaggerApi
find AUTOBUILD/javaBalancerClient/src/ -type f | xargs git update-index --skip-worktree
Finally, apply the patch
cd swaggerApi
git apply ../swaggerApi.patch
Make sure that local.properties contains sdk.dir property set to your Android SDK absolute path.
You can build debug apk with Gradle by executing ./gradlew assembleDebug on Linux and gradlew assembleDebug on Windows.