Add panic to sim time examples

r2r/examples/sim_time_publisher.rs

@@ -32,4 +32,5 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
 
 #[cfg(not(r2r__rosgraph_msgs__msg__Clock))]
 fn main() {
+    panic!("Sim_time_publisher example is not compiled with 'rosgraph_msgs'.");
 }

r2r/examples/timer_sim_time.rs

@@ -33,6 +33,7 @@ async fn timer_task(
 
 /// Publication of time can be done either using the example `sim_time_publisher`
 /// or with `ros2 bag play --clock <clock_frequency> <the_bag>`
+#[cfg(r2r__rosgraph_msgs__msg__Clock)]
 fn main() -> Result<(), Box<dyn std::error::Error>> {
     let ctx = r2r::Context::create()?;
     let mut node = r2r::Node::create(ctx, "testnode", "")?;
@@ -80,3 +81,8 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
 
     Ok(())
 }
+
+#[cfg(not(r2r__rosgraph_msgs__msg__Clock))]
+fn main() {
+    panic!("Timer_sim_time example is not compiled with 'rosgraph_msgs'.");
+}