Extract extensions to a separate directory....

src/SConscript

 # Copyright 2008 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 101 matching lines @@
     type-info.cc
     unicode.cc
     utils.cc
     v8-counters.cc
     v8.cc
     v8threads.cc
     variables.cc
     version.cc
     virtual-frame.cc
     zone.cc
+    extensions/gc-extension.cc
+    extensions/externalize-string-extension.cc
     """),
   'arch:arm': Split("""
     jump-target-light.cc
     virtual-frame-light.cc
     arm/builtins-arm.cc
     arm/code-stubs-arm.cc
     arm/codegen-arm.cc
     arm/constants-arm.cc
     arm/cpu-arm.cc
     arm/debug-arm.cc
@@ skipping 189 matching lines @@
       snapshot_cc = 'snapshot.cc'
     snapshot_obj = context.ConfigureObject(env, snapshot_cc, CPPPATH=['.'])
   else:
     snapshot_obj = empty_snapshot_obj
   library_objs = [non_snapshot_files, libraries_obj, snapshot_obj]
   return (library_objs, d8_objs, [mksnapshot])
 
 
 (library_objs, d8_objs, mksnapshot) = ConfigureObjectFiles()
 Return('library_objs d8_objs mksnapshot')