Clean up multi byte nop support on x64 to more closely match IA32.

test/cctest/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 92 matching lines @@
     'test-assembler-arm.cc',
     'test-disasm-arm.cc'
   ],
   'arch:ia32': [
     'test-assembler-ia32.cc',
     'test-disasm-ia32.cc',
     'test-log-stack-tracer.cc'
   ],
   'arch:x64': ['test-assembler-x64.cc',
                'test-macro-assembler-x64.cc',
-               'test-log-stack-tracer.cc'],
+               'test-log-stack-tracer.cc',
+               'test-disasm-x64.cc'],
   'arch:mips': ['test-assembler-mips.cc',
                 'test-disasm-mips.cc'],
   'os:linux':  ['test-platform-linux.cc'],
   'os:macos':  ['test-platform-macos.cc'],
   'os:nullos': ['test-platform-nullos.cc'],
   'os:win32':  ['test-platform-win32.cc']
 }
 
 
 def Build():
@@ skipping 13 matching lines @@
   # 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.
   object_files.append(js_files_obj)
   return env.Program('cctest', ['cctest.cc', cctest_files, object_files],
       PDB='cctest.exe.pdb')
 
 
 program = Build()
 Return('program')