MYAPP_RELEASE_STORE_FILE=filename.jks
MYAPP_RELEASE_KEY_ALIAS=your-key-alias
MYAPP_RELEASE_STORE_PASSWORD=your-store-password
MYAPP_RELEASE_KEY_PASSWORD=your-release-key-password

signingConfigs{
    release {
        if (project.hasProperty('MYAPP_RELEASE_STORE_FILE')) {
            storeFile file(MYAPP_RELEASE_STORE_FILE)
            storePassword MYAPP_RELEASE_STORE_PASSWORD
            keyAlias MYAPP_RELEASE_KEY_ALIAS
            keyPassword MYAPP_RELEASE_KEY_PASSWORD
        }
    }
}

buildTypes {
    release {
        signingConfig signingConfigs.release
    }
}