Disable x64 disassembler under win32.

runtime/vm/vm_sources.gypi

 # Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 # for details. All rights reserved. Use of this source code is governed by a
 # BSD-style license that can be found in the LICENSE file.
 
 # This file contains all sources (vm and tests) for the dart virtual machine.
 # Unit test files need to have a '_test' suffix appended to the name.
 {
   'sources': [
     'allocation.cc',
     'allocation.h',
     'allocation_test.cc',
     'assembler.cc',
     'assembler.h',
     'assembler_arm.h',
     'assembler_ia32.cc',
     'assembler_ia32.h',
     'assembler_ia32_test.cc',
     'assembler_macros.h',
     'assembler_macros_ia32.cc',
     'assembler_macros_ia32.h',
+    'assembler_macros_x64.cc',
+    'assembler_macros_x64.h',
     'assembler_x64.cc',
     'assembler_x64.h',
     'assembler_x64_test.cc',
     'assert.cc',
     'assert.h',
     'assert_test.cc',
     'ast.cc',
     'ast.h',
     'ast_test.cc',
     'ast_printer.h',
@@ skipping 213 matching lines @@
     'virtual_memory_test.cc',
     'virtual_memory_win.cc',
     'verifier.cc',
     'verifier.h',
     'visitor.h',
     'zone.cc',
     'zone.h',
     'zone_test.cc',
   ],
 }