Rename TARGET_OS_* to HOST_OS_*.

runtime/vm/cpuinfo_macos.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_MACOS)
+#if defined(HOST_OS_MACOS)
 
 #include "vm/cpuinfo.h"
 
 #include <errno.h>       // NOLINT
 #include <sys/types.h>   // NOLINT
 #include <sys/sysctl.h>  // NOLINT
 
 #include "platform/assert.h"
 
 namespace dart {
@@ skipping 56 matching lines @@
 
 bool CpuInfo::HasField(const char* field) {
   ASSERT(method_ != kCpuInfoDefault);
   ASSERT(field != NULL);
   int ret = sysctlbyname(field, NULL, NULL, NULL, 0);
   return (ret == 0);
 }
 
 }  // namespace dart
 
-#endif  // defined(TARGET_OS_MACOS)
+#endif  // defined(HOST_OS_MACOS)