Rename TARGET_OS_* to HOST_OS_*.

runtime/vm/proccpuinfo.h

 // 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.
 
 #ifndef RUNTIME_VM_PROCCPUINFO_H_
 #define RUNTIME_VM_PROCCPUINFO_H_
 
 #include "vm/globals.h"
-#if defined(TARGET_OS_LINUX) || defined(TARGET_OS_ANDROID)
+#if defined(HOST_OS_LINUX) || defined(HOST_OS_ANDROID)
 
 #include "vm/allocation.h"
 
 namespace dart {
 
 class ProcCpuInfo : public AllStatic {
  public:
   static void InitOnce();
   static void Cleanup();
   static bool FieldContains(const char* field, const char* search_string);
   static const char* ExtractField(const char* field);
   static bool HasField(const char* field);
 
  private:
   static char* data_;
   static intptr_t datalen_;
 
   static char* FieldStart(const char* field);
 };
 
 }  // namespace dart
 
-#endif  // defined(TARGET_OS_LINUX) || defined(TARGET_OS_ANDROID)
+#endif  // defined(HOST_OS_LINUX) || defined(HOST_OS_ANDROID)
 
 #endif  // RUNTIME_VM_PROCCPUINFO_H_