Introduce mkgrokdump to update tools/v8heapconst.py.

tools/mkgrokdump.gyp

+# Copyright 2017 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,
+    'v8_enable_i18n_support%': 1,
+  },
+  'includes': ['../gypfiles/toolchain.gypi', '../gypfiles/features.gypi'],
+  'targets': [
+    {
+      'target_name': 'mkgrokdump',
+      'type': 'executable',
+      'dependencies': [
+        '../src/v8.gyp:v8',
+        '../src/v8.gyp:v8_libbase',
+        '../src/v8.gyp:v8_libplatform',
+      ],
+      'conditions': [
+        ['v8_enable_i18n_support==1', {
+          'dependencies': [
+            '<(icu_gyp_path):icui18n',
+            '<(icu_gyp_path):icuuc',
+          ],
+        }],
+      ],
+      'include_dirs+': [
+        '..',
+      ],
+      'sources': [
+        'mkgrokdump.cc',
+      ],
+    },
+  ],
+}