Avoid fallback to weak entropy for the PRNGs on Windows.

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 787 matching lines @@
             ],
           }
         ],
         ['OS=="mac"', {
           'sources': [
             '../../src/platform-macos.cc',
             '../../src/platform-posix.cc'
           ]},
         ],
         ['OS=="win"', {
+          'defines': [
+            '_CRT_RAND_S'  # for rand_s()
+          ],
           'variables': {
             'gyp_generators': '<!(echo $GYP_GENERATORS)',
           },
           'conditions': [
             ['gyp_generators=="make"', {
               'variables': {
                 'build_env': '<!(uname -o)',
               },
               'conditions': [
                 ['build_env=="Cygwin"', {
@@ skipping 223 matching lines @@
         }],
         ['v8_compress_startup_data=="bz2"', {
           'libraries': [
             '-lbz2',
           ]
         }],
       ],
     },
   ],
 }