Ignore a threaded test on emscripten

Author: alexcrichton

src/test/run-pass/generator/smoke.rs

@@ -8,6 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// ignore-emscripten
 // compile-flags: --test
 
 #![feature(generators, generator_trait)]