Prepares for arm64 cross-build.

runtime/vm/os_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 "vm/globals.h"
 #if defined(TARGET_OS_LINUX)
 
 #include "vm/os.h"
 
 #include <errno.h>  // NOLINT
@@ skipping 648 matching lines @@
     req = rem;
   }
 }
 
 
 void OS::DebugBreak() {
 #if defined(HOST_ARCH_X64) || defined(HOST_ARCH_IA32)
   asm("int $3");
 #elif defined(HOST_ARCH_ARM)
   asm("svc #0x9f0001");  // __ARM_NR_breakpoint
-#elif defined(HOST_ARCH_MIPS)
+#elif defined(HOST_ARCH_MIPS) || defined(HOST_ARCH_ARM64)
   UNIMPLEMENTED();
 #else
 #error Unsupported architecture.
 #endif
 }
 
 
 char* OS::StrNDup(const char* s, intptr_t n) {
   return strndup(s, n);
 }
@@ skipping 99 matching lines @@
 }
 
 
 void OS::Exit(int code) {
   exit(code);
 }
 
 }  // namespace dart
 
 #endif  // defined(TARGET_OS_LINUX)