Rename TARGET_OS_* to HOST_OS_*.

runtime/vm/virtual_memory_win.cc

 // Copyright (c) 2012, 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.
 
 #include "vm/globals.h"
-#if defined(TARGET_OS_WINDOWS)
+#if defined(HOST_OS_WINDOWS)
 
 #include "vm/virtual_memory.h"
 
 #include "platform/assert.h"
 #include "vm/os.h"
 
 #include "vm/isolate.h"
 
 namespace dart {
 
@@ skipping 74 matching lines @@
       break;
   }
   DWORD old_prot = 0;
   bool result = VirtualProtect(reinterpret_cast<void*>(page_address),
                                end_address - page_address, prot, &old_prot);
   return result;
 }
 
 }  // namespace dart
 
-#endif  // defined(TARGET_OS_WINDOWS)
+#endif  // defined(HOST_OS_WINDOWS)