add compile error

src/lib.rs

@@ -28,6 +28,9 @@ mod tests;
 
 cfg_if! {
     if #[cfg(feature = "multicore")] {
+        #[cfg(feature = "wasm")]
+        compile_error!("Multicore feature is not yet compatible with wasm target arch");
+
         mod multicore;
         mod worker {
             pub use crate::multicore::*;