Fix Gyp rule that broke node.js build after snapshot log removal.

tools/gyp/v8.gyp

 # Copyright 2012 the V8 project authors. All rights reserved.
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 #       notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
 #       copyright notice, this list of conditions and the following
 #       disclaimer in the documentation and/or other materials provided
@@ skipping 193 matching lines @@
           'action_name': 'run_mksnapshot',
           'inputs': [
             '<(mksnapshot_exec)',
             '<(embed_script)',
             '<(warmup_script)',
           ],
           'outputs': [
             '<(INTERMEDIATE_DIR)/snapshot.cc',
           ],
           'variables': {
+            'mksnapshot_flags': [],
             'conditions': [
               ['v8_random_seed!=0', {
                 'mksnapshot_flags': ['--random-seed', '<(v8_random_seed)'],
               }],
               ['v8_vector_stores!=0', {
                 'mksnapshot_flags': ['--vector-stores'],
               }],
             ],
           },
           'action': [
@@ skipping 139 matching lines @@
           ],
           'sources': [
             '../../src/snapshot/natives-external.cc',
             '../../src/snapshot/snapshot-external.cc',
           ],
           'actions': [
             {
               'action_name': 'run_mksnapshot (external)',
               'inputs': ['<(mksnapshot_exec)'],
               'variables': {
+                'mksnapshot_flags': [],
                 'conditions': [
                   ['v8_random_seed!=0', {
                     'mksnapshot_flags': ['--random-seed', '<(v8_random_seed)'],
                   }],
                   ['v8_vector_stores!=0', {
                     'mksnapshot_flags': ['--vector-stores'],
                   }],
                 ],
               },
               'conditions': [
@@ skipping 1887 matching lines @@
         }],
         ['want_separate_host_toolset==1', {
           'toolsets': ['host'],
         }, {
           'toolsets': ['target'],
         }],
       ],
     },
   ],
 }