Fix shared library build errors.

SConstruct

 # 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 83 matching lines @@
       'CCFLAGS':      ['-g', '-O0'],
       'CPPDEFINES':   ['ENABLE_DISASSEMBLER', 'DEBUG'],
     },
     'mode:release': {
       'CCFLAGS':      ['-O3', '-fomit-frame-pointer', '-fdata-sections',
                        '-ffunction-sections'],
     },
     'os:linux': {
       'CCFLAGS':      ['-ansi'] + GCC_EXTRA_CCFLAGS,
       'library:shared': {
-        'CPPDEFINES': ['V8_SHARED'],
+        'CPPDEFINES': ['V8_SHARED', 'BUILDING_V8_SHARED'],
         'LIBS': ['pthread']
       }
     },
     'os:macos': {
       'CCFLAGS':      ['-ansi', '-mmacosx-version-min=10.4'],
       'library:shared': {
-        'CPPDEFINES': ['V8_SHARED']
+        'CPPDEFINES': ['V8_SHARED', 'BUILDING_V8_SHARED'],
       }
     },
     'os:freebsd': {
       'CPPPATH' : [src_dir, '/usr/local/include'],
       'LIBPATH' : ['/usr/local/lib'],
       'CCFLAGS':      ['-ansi'],
       'LIBS': ['execinfo']
     },
     'os:openbsd': {
       'CPPPATH' : [src_dir, '/usr/local/include'],
@@ skipping 1486 matching lines @@
 #  will not work much longer. Please switch to using  #
 #  the GYP-based build now. Instructions are at       #
 #  http://code.google.com/p/v8/wiki/BuildingWithGYP.  #
 #######################################################
   """
 
 WarnAboutDeprecation()
 import atexit
 atexit.register(WarnAboutDeprecation)
 Build()