Ignore lots and lots of std tests on emscripten

src/liballoc/arc.rs

@@ -1000,6 +1000,7 @@ mod tests {
     }
 
     #[test]
+    #[cfg_attr(target_os = "emscripten", ignore)]
     fn manually_share_arc() {
         let v = vec![1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
         let arc_v = Arc::new(v);