Make arm32 cpu detection recognize the DragonBoard as arm64.

runtime/vm/cpuinfo_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 "vm/globals.h"
 #if defined(TARGET_OS_MACOS)
 
 #include "vm/cpuinfo.h"
 
 #include <errno.h>       // NOLINT
 #include <sys/types.h>   // NOLINT
 #include <sys/sysctl.h>  // NOLINT
 
 #include "platform/assert.h"
 
 namespace dart {
 
 CpuInfoMethod CpuInfo::method_ = kCpuInfoDefault;
 const char* CpuInfo::fields_[kCpuInfoMax] = {0};
 
 void CpuInfo::InitOnce() {
   method_ = kCpuInfoSystem;
 
   fields_[kCpuInfoProcessor] = "machdep.cpu.vendor";
   fields_[kCpuInfoModel] = "machdep.cpu.brand_string";
   fields_[kCpuInfoHardware] = "machdep.cpu.brand_string";
   fields_[kCpuInfoFeatures] = "machdep.cpu.features";
+  fields_[kCpuInfoArchitecture] = NULL;
 }
 
 
 void CpuInfo::Cleanup() {}
 
 
 bool CpuInfo::FieldContains(CpuInfoIndices idx, const char* search_string) {
   ASSERT(method_ != kCpuInfoDefault);
   ASSERT(search_string != NULL);
   const char* field = FieldName(idx);
@@ skipping 35 matching lines @@
 bool CpuInfo::HasField(const char* field) {
   ASSERT(method_ != kCpuInfoDefault);
   ASSERT(field != NULL);
   int ret = sysctlbyname(field, NULL, NULL, NULL, 0);
   return (ret == 0);
 }
 
 }  // namespace dart
 
 #endif  // defined(TARGET_OS_MACOS)