Rename TARGET_OS_* to HOST_OS_*.

runtime/vm/signal_handler_win.cc

 // Copyright (c) 2013, 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"
 #include "vm/signal_handler.h"
-#if defined(TARGET_OS_WINDOWS)
+#if defined(HOST_OS_WINDOWS)
 
 namespace dart {
 
 uintptr_t SignalHandler::GetProgramCounter(const mcontext_t& mcontext) {
   UNIMPLEMENTED();
   return 0;
 }
 
 
 uintptr_t SignalHandler::GetFramePointer(const mcontext_t& mcontext) {
@@ skipping 25 matching lines @@
 }
 
 
 void SignalHandler::Remove() {
   UNIMPLEMENTED();
 }
 
 
 }  // namespace dart
 
-#endif  // defined(TARGET_OS_WINDOWS)
+#endif  // defined(HOST_OS_WINDOWS)