Rename TARGET_OS_* to HOST_OS_*.

runtime/vm/cpu_arm64.cc

 // Copyright (c) 2014, 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_ARCH_ARM64)
 
 #include "vm/cpu.h"
 #include "vm/cpu_arm64.h"
 
 #include "vm/cpuinfo.h"
 #include "vm/simulator.h"
 
 #if !defined(USING_SIMULATOR)
 #include <sys/syscall.h> /* NOLINT */
 #include <unistd.h>      /* NOLINT */
 #endif
 
 namespace dart {
 
 void CPU::FlushICache(uword start, uword size) {
-#if TARGET_OS_IOS
+#if HOST_OS_IOS
   // Precompilation never patches code so there should be no I cache flushes.
   UNREACHABLE();
 #endif
 
-#if !defined(USING_SIMULATOR) && !TARGET_OS_IOS
+#if !defined(USING_SIMULATOR) && !HOST_OS_IOS
   // Nothing to do. Flushing no instructions.
   if (size == 0) {
     return;
   }
 
 // ARM recommends using the gcc intrinsic __clear_cache on Linux and Android.
 // blogs.arm.com/software-enablement/141-caches-and-self-modifying-code/
-#if defined(TARGET_OS_ANDROID) || defined(TARGET_OS_FUCHSIA) ||                \
-    defined(TARGET_OS_LINUX)
+#if defined(HOST_OS_ANDROID) || defined(HOST_OS_FUCHSIA) ||                    \
+    defined(HOST_OS_LINUX)
   extern void __clear_cache(char*, char*);
   char* beg = reinterpret_cast<char*>(start);
   char* end = reinterpret_cast<char*>(start + size);
   ::__clear_cache(beg, end);
 #else
 #error FlushICache only tested/supported on Android, Fuchsia, and Linux
 #endif
 
 #endif
 }
@@ skipping 54 matching lines @@
   ASSERT(hardware_ != NULL);
   free(const_cast<char*>(hardware_));
   hardware_ = NULL;
   CpuInfo::Cleanup();
 }
 #endif  // !defined(USING_SIMULATOR)
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_ARM64