Rename TARGET_OS_* to HOST_OS_*.

runtime/bin/crypto_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 "platform/globals.h"
-#if defined(TARGET_OS_MACOS)
+#if defined(HOST_OS_MACOS)
 
 #include <errno.h>  // NOLINT
 #include <fcntl.h>  // NOLINT
 
 #include "bin/crypto.h"
 #include "bin/fdutils.h"
 #include "platform/signal_blocker.h"
 
 namespace dart {
 namespace bin {
@@ skipping 17 matching lines @@
     }
     bytes_read += res;
   } while (bytes_read < count);
   VOID_TEMP_FAILURE_RETRY_NO_SIGNAL_BLOCKER(close(fd));
   return true;
 }
 
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(TARGET_OS_MACOS)
+#endif  // defined(HOST_OS_MACOS)