Fix warnings in raytrace-parallel example

examples/raytrace-parallel/src/pool.rs

@@ -1,3 +1,7 @@
+// Silences warnings from the compiler about Work.func and child_entry_point
+// being unused when the target is not wasm.
+#![cfg_attr(not(target_arch = "wasm32"), allow(dead_code))]
+
 //! A small module that's intended to provide an example of creating a pool of
 //! web workers which can be used to execute `rayon`-style work.