Introduce -m64 flag for making x64 when the default gcc compiler is for X32

build/common.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 434 matching lines @@
                 'cflags': [ '<(m32flag)' ],
                 'ldflags': [ '<(m32flag)' ],
               }],
             ],
             'xcode_settings': {
               'ARCHS': [ 'i386' ],
             },
           }],
         ],
       }],
+      ['(OS=="linux") and (v8_target_arch=="x64")', {
+        # Check whether the host compiler and target compiler support the
+        # '-m64' option and set it if so.
+        'target_conditions': [
+          ['_toolset=="host"', {
+            'variables': {
+              'm64flag': '<!((echo | $(echo ${CXX_host:-$(which g++)}) -m64 -E - > /dev/null 2>&1) && echo "-m64" || true)',
+            },
+            'cflags': [ '<(m64flag)' ],
+            'ldflags': [ '<(m64flag)' ],
+          }],
+          ['_toolset=="target"', {
+            'variables': {
+              'm64flag': '<!((echo | $(echo ${CXX_target:-<(CXX)}) -m64 -E - > /dev/null 2>&1) && echo "-m64" || true)',
+            },
+            'cflags': [ '<(m64flag)' ],
+            'ldflags': [ '<(m64flag)' ],
+          }]
+        ],
+      }],
       ['OS=="freebsd" or OS=="openbsd"', {
         'cflags': [ '-I/usr/local/include' ],
       }],
       ['OS=="netbsd"', {
         'cflags': [ '-I/usr/pkg/include' ],
       }],
     ],  # conditions
     'configurations': {
       'Debug': {
         'variables': {
@@ skipping 137 matching lines @@
                 'OptimizeReferences': '2',
                 'EnableCOMDATFolding': '2',
               },
             },
           }],  # OS=="win"
         ],  # conditions
       },  # Release
     },  # configurations
   },  # target_defaults
 }