Remove mips64 defines from darwin-specific file

lib/sanitizer_common/sanitizer_stoptheworld_mac.cc

 //===-- sanitizer_stoptheworld_mac.cc -------------------------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // See sanitizer_stoptheworld.h for details.
 //
 //===----------------------------------------------------------------------===//
 
 #include "sanitizer_platform.h"
 
 #if SANITIZER_MAC && (defined(__x86_64__) || defined(__aarch64__) || \
-                      defined(__mips64) || defined(__i386))
+                      defined(__i386))
 
 #include <mach/mach.h>
 
 #include "sanitizer_stoptheworld.h"
 
 namespace __sanitizer {
 typedef struct {
   tid_t tid;

 }
 
 uptr SuspendedThreadsListMac::RegisterCount() const {
   return THREAD_STATE_COUNT;
 }
 } // namespace __sanitizer
 
 #endif  // SANITIZER_MAC && (defined(__x86_64__) || defined(__aarch64__)) ||
-        //                   defined(__mips64) || defined(__i386))
+        //                   defined(__i386))