Fixed a known issue in D8 (read file), enabled D8 shared library build on Windows.

SConstruct

 # Copyright 2011 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 1376 matching lines @@
     library_name += '-' + version
 
   # Generate library SONAME if required by the build.
   if context.options['soname'] == 'on':
     soname = GetSpecificSONAME()
     if soname == '':
       soname = 'lib' + library_name + '.so'
     env['SONAME'] = soname
 
   # Build the object files by invoking SCons recursively.
+  d8_env = Environment(tools=tools)
+  d8_env.Replace(**context.flags['d8'])
   (object_files, shell_files, mksnapshot, preparser_files) = env.SConscript(
     join('src', 'SConscript'),
     build_dir=join('obj', target_id),
-    exports='context tools',
+    exports='context tools d8_env',
     duplicate=False
   )
 
   context.mksnapshot_targets.append(mksnapshot)
 
   # Link the object files into a library.
   env.Replace(**context.flags['v8'])
 
   context.ApplyEnvOverrides(env)
   if context.options['library'] == 'static':
     library = env.StaticLibrary(library_name, object_files)
     preparser_library = env.StaticLibrary(preparser_library_name,
                                           preparser_files)
   else:
     # There seems to be a glitch in the way scons decides where to put
     # PDB files when compiling using MSVC so we specify it manually.
     # This should not affect any other platforms.
     pdb_name = library_name + '.dll.pdb'
     library = env.SharedLibrary(library_name, object_files, PDB=pdb_name)
     preparser_pdb_name = preparser_library_name + '.dll.pdb';
     preparser_soname = 'lib' + preparser_library_name + '.so';
     preparser_library = env.SharedLibrary(preparser_library_name,
                                           preparser_files,
                                           PDB=preparser_pdb_name,
                                           SONAME=preparser_soname)
   context.library_targets.append(library)
   context.library_targets.append(preparser_library)
 
-  d8_env = Environment(tools=tools)
-  d8_env.Replace(**context.flags['d8'])
   context.ApplyEnvOverrides(d8_env)
   if context.options['library'] == 'static':
     shell = d8_env.Program('d8' + suffix, object_files + shell_files)
   else:
     shell = d8_env.Program('d8' + suffix, shell_files)
     d8_env.Depends(shell, library)
   context.d8_targets.append(shell)
 
   for sample in context.samples:
     sample_env = Environment(tools=tools)
@@ skipping 86 matching lines @@
 # version of scons.  Also, there's a bug in some revisions that
 # doesn't allow this flag to be set, so we swallow any exceptions.
 # Lovely.
 try:
   SetOption('warn', 'no-deprecated')
 except:
   pass
 
 
 Build()