gradle script using global properties in signing config

build.gradle

// ...
android {
    signingConfigs {
        release {
            if (project.hasProperty('RELEASE_STORE_FILE')) {
                storeFile file(RELEASE_STORE_FILE)
                storePassword RELEASE_STORE_PASSWORD
                keyAlias RELEASE_KEY_ALIAS
                keyPassword RELEASE_KEY_PASSWORD
            }
        }
        debug {
            if (project.hasProperty('DEBUG_STORE_FILE')) {
                storeFile file(DEBUG_STORE_FILE)
                storePassword DEBUG_STORE_PASSWORD
                keyAlias DEBUG_KEY_ALIAS
                keyPassword DEBUG_KEY_PASSWORD
            }
        }
    }
    // ...
}