Fix simarm64 build on Mac OS X

runtime/vm/disassembler_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/disassembler.h"
 
 #include "vm/globals.h"  // Needed here to get TARGET_ARCH_ARM64.
 #if defined(TARGET_ARCH_ARM64)
 #include "platform/assert.h"
 
@@ skipping 75 matching lines @@
   "r8",  "r9",  "r10", "r11", "r12", "r13", "r14", "r15",
   "r16", "r17", "r18", "r19", "r20", "r21", "r22", "r23",
   "r24", "ip0", "ip1", "pp",  "ctx", "fp",  "lr",  "r31",
 };
 
 
 // Print the register name according to the active name converter.
 void ARM64Decoder::PrintRegister(int reg, R31Type r31t) {
   ASSERT(0 <= reg);
   ASSERT(reg < kNumberOfCpuRegisters);
-  if ((reg == 31)) {
+  if (reg == 31) {
     const char* rstr = (r31t == R31IsZR) ? "zr" : "sp";
     Print(rstr);
   } else {
     Print(reg_names[reg]);
   }
 }
 
 
 // These shift names are defined in a way to match the native disassembler
 // formatting. See for example the command "objdump -d <binary file>".
@@ skipping 497 matching lines @@
                                   human_buffer,
                                   sizeof(human_buffer),
                                   pc);
     pc += instruction_length;
   }
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_ARM