[gn] Add unittests

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.
 
+# Please keep this file in sync with BUILD.gn.
+
 {
   'variables': {
     'v8_code': 1,
   },
   'includes': ['../../gypfiles/toolchain.gypi', '../../gypfiles/features.gypi'],
   'targets': [
     {
       'target_name': 'unittests',
       'type': 'executable',
       'variables': {
@@ skipping 203 matching lines @@
             '../../gypfiles/isolate.gypi',
           ],
           'sources': [
             'unittests.isolate',
           ],
         },
       ],
     }],
   ],
 }