Allowing optional build of a WASM prototype behind a gyp define.

test/unittests/unittests.gyp

 # Copyright 2014 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.
 
 {
   'variables': {
     'v8_code': 1,
   },
   'includes': ['../../build/toolchain.gypi', '../../build/features.gypi'],
   'targets': [
@@ skipping 145 matching lines @@
           # that show up because we use -std=gnu++0x instead of -std=c++11.
           'cflags!': [
             '-pedantic',
           ],
           'direct_dependent_settings': {
             'cflags!': [
               '-pedantic',
             ],
           },
         }],
+        ['v8_wasm!=0', {
+          'dependencies': [
+            '../../third_party/wasm/test/unittests/wasm/wasm.gyp:wasm_unittests',
+          ],
+        }],
       ],
     },
   ],
 }