[linux] Use _GLIBCXX_DEBUG in Debug builds by default for better checking.

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 159 matching lines @@
   },
   'target_defaults': {
     'variables': {
       'v8_code%': '<(v8_code)',
     },
     'default_configuration': 'Debug',
     'configurations': {
       'DebugBaseCommon': {
         'cflags': [ '-g', '-O0' ],
         'conditions': [
-          ['(v8_target_arch=="ia32" or v8_target_arch=="x87") and \
-            OS=="linux"', {
-            'defines': [
-              '_GLIBCXX_DEBUG'
-            ],
-          }],
           [ 'OS=="aix"', {
             'cflags': [ '-gxcoff' ],
           }],
         ],
       },
       'Optdebug': {
         'inherit_from': [ 'DebugBaseCommon', 'DebugBase1' ],
       },
       'Debug': {
         # Xcode insists on this empty entry.
@@ skipping 326 matching lines @@
     ['use_goma==1 and ("<(GENERATOR)"=="ninja" or clang==1)', {
       'make_global_settings': [
        ['CC_wrapper', '<(gomadir)/gomacc'],
        ['CXX_wrapper', '<(gomadir)/gomacc'],
        ['CC.host_wrapper', '<(gomadir)/gomacc'],
        ['CXX.host_wrapper', '<(gomadir)/gomacc'],
       ],
     }],
   ],
 }