Fix unsimulated ARM64 build.

runtime/vm/signal_handler_linux.cc

 // Copyright (c) 2013, 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"
 #include "vm/simulator.h"
 #include "vm/signal_handler.h"
 #if defined(TARGET_OS_LINUX)
 
 namespace dart {
@@ skipping 95 matching lines @@
   lr = 0;
 #elif defined(TARGET_ARCH_MIPS) && defined(USING_SIMULATOR)
   lr = 0;
 #elif defined(TARGET_ARCH_ARM) && defined(USING_SIMULATOR)
   lr = 0;
 #elif defined(TARGET_ARCH_ARM64) && defined(USING_SIMULATOR)
   lr = 0;
 #elif defined(TARGET_ARCH_ARM)
   lr = static_cast<uintptr_t>(mcontext.arm_lr);
 #elif defined(TARGET_ARCH_ARM64)
-  lr = static_cast<uintptr_t>(mcontext.lr);
+  lr = static_cast<uintptr_t>(mcontext.regs[30]);
 #elif defined(TARGET_ARCH_MIPS)
   lr = static_cast<uintptr_t>(mcontext.gregs[31]);
 #else
   UNIMPLEMENTED();
 #endif  // TARGET_ARCH_...
   return lr;
 }
 
 
 void SignalHandler::Install(SignalAction action) {
@@ skipping 15 matching lines @@
   sigemptyset(&act.sa_mask);
   act.sa_flags = 0;
   int r = sigaction(SIGPROF, &act, NULL);
   ASSERT(r == 0);
 }
 
 
 }  // namespace dart
 
 #endif  // defined(TARGET_OS_LINUX)