Add -Wno-sign-compare flag to gcc builds.

build/standalone.gypi

 # 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 388 matching lines @@
           'Debug_x64': {
             'inherit_from': ['Debug'],
           },
           'Release_x64': {
             'inherit_from': ['Release'],
           },
         }],
       ],
     },
     'conditions':[
+      ['clang==0', {
+        'cflags+': ['-Wno-sign-compare',],
+      }],
       ['(clang==1 or host_clang==1) and OS!="win"', {
         # This is here so that all files get recompiled after a clang roll and
         # when turning clang on or off.
         # (defines are passed via the command line, and build systems rebuild
         # things when their commandline changes). Nothing should ever read this
         # define.
         'defines': ['CR_CLANG_REVISION=<!(<(DEPTH)/tools/clang/scripts/update.sh --print-revision)'],
         'conditions': [
           ['host_clang==1', {
             'target_conditions': [
@@ skipping 914 matching lines @@
               '-fsanitize=cfi-vcall',
               '-fsanitize=cfi-derived-cast',
               '-fsanitize=cfi-unrelated-cast',
             ],
           }],
         ],
       },
     }],
   ],
 }