Rename TARGET_OS_* to HOST_OS_*.

runtime/bin/utils_linux.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_LINUX)
+#if defined(HOST_OS_LINUX)
 
 #include <errno.h>     // NOLINT
 #include <netdb.h>     // NOLINT
 #include <sys/time.h>  // NOLINT
 #include <time.h>      // NOLINT
 
 #include "bin/utils.h"
 #include "platform/assert.h"
 #include "platform/utils.h"
 
@@ skipping 105 matching lines @@
     // We should only ever see an interrupt error.
     ASSERT(errno == EINTR);
     // Copy remainder into requested and repeat.
     req = rem;
   }
 }
 
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(TARGET_OS_LINUX)
+#endif  // defined(HOST_OS_LINUX)