Supress warning for Array.compare

Change-Id: I60847b035baab185ca93071f8953e4e1fb521319

user/super/com/google/gwt/emul/java/util/Arrays.java

diff --git a/user/super/com/google/gwt/emul/java/util/Arrays.java b/user/super/com/google/gwt/emul/java/util/Arrays.java
index a9dd2a4..f3e1e4e 100644
--- a/user/super/com/google/gwt/emul/java/util/Arrays.java
+++ b/user/super/com/google/gwt/emul/java/util/Arrays.java
@@ -1774,6 +1774,7 @@
 
   @JsFunction
   private interface CompareLongFunction {
+    @SuppressWarnings("unusable-by-js")
     int compare(long d1, long d2);
   }