Rename TARGET_OS_* to HOST_OS_*.

runtime/vm/atomic_win.h

 // 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.
 
 #ifndef RUNTIME_VM_ATOMIC_WIN_H_
 #define RUNTIME_VM_ATOMIC_WIN_H_
 
 #if !defined RUNTIME_VM_ATOMIC_H_
 #error Do not include atomic_win.h directly. Use atomic.h instead.
 #endif
 
-#if !defined(TARGET_OS_WINDOWS)
+#if !defined(HOST_OS_WINDOWS)
 #error This file should only be included on Windows builds.
 #endif
 
 namespace dart {
 
 inline uintptr_t AtomicOperations::FetchAndIncrement(uintptr_t* p) {
 #if defined(HOST_ARCH_X64)
   return static_cast<uintptr_t>(
              InterlockedIncrement64(reinterpret_cast<LONGLONG*>(p))) -
          1;
@@ skipping 111 matching lines @@
       static_cast<LONG>(old_value)));
 #else
 #error Unsupported host architecture.
 #endif
 }
 #endif  // !defined(USING_SIMULATOR)
 
 }  // namespace dart
 
 #endif  // RUNTIME_VM_ATOMIC_WIN_H_