Add --enable-wasm to wasm tests.

test/mjsunit/wasm/unreachable.js

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// Flags: --expose-wasm
+
 load("test/mjsunit/wasm/wasm-constants.js");
 
 var module = (function () {
   var kFuncWithBody = 9;
   var kFuncImported = 7;
   var kBodySize1 = 1;
   var kMainOffset = 6 + kFuncWithBody + kBodySize1 + 1;
 
   var ffi = new Object();
   ffi.add = (function(a, b) { return a + b | 0; });
@@ skipping 22 matching lines @@
 assertEquals("function", typeof module.main);
 
 var exception = "";
 try {
     assertEquals(0, module.main());
 } catch(e) {
     print("correctly caught: " + e);
     exception = e;
 }
 assertEquals("unreachable", exception);