Use opt-level 3 for smoldot and local target build

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

examples/examples/unstable_light_client_tx_basic.rs

@@ -8,6 +8,8 @@ pub mod polkadot {}
 
 #[tokio::main]
 async fn main() -> Result<(), Box<dyn std::error::Error>> {
+    tracing_subscriber::fmt::init();
+
     // Create a light client from the provided chain spec.
     //
     // # Note