Rename TARGET_OS_* to HOST_OS_*.

runtime/bin/process_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.
 
 #if !defined(DART_IO_DISABLED)
 
 #include "platform/globals.h"
-#if defined(TARGET_OS_WINDOWS)
+#if defined(HOST_OS_WINDOWS)
 
 #include "bin/process.h"
 
 #include <process.h>  // NOLINT
 
 #include "bin/builtin.h"
 #include "bin/dartutils.h"
 #include "bin/eventhandler.h"
 #include "bin/lockers.h"
 #include "bin/log.h"
@@ skipping 1019 matching lines @@
     if (signal_handlers == NULL) {
       USE(SetConsoleCtrlHandler(SignalHandler, false));
     }
   }
   delete handler;
 }
 
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(TARGET_OS_WINDOWS)
+#endif  // defined(HOST_OS_WINDOWS)
 
 #endif  // !defined(DART_IO_DISABLED)