Fix win32 build breakage

runtime/vm/os_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/os.h"
 
 #include <errno.h>
 #include <limits.h>
 #include <mach/mach.h>
 #include <mach/clock.h>
@@ skipping 54 matching lines @@
     return 0;
   }
   return (static_cast<int64_t>(tv.tv_sec) * 1000000) + tv.tv_usec;
 }
 
 
 void* OS::AlignedAllocate(intptr_t size, intptr_t alignment) {
   const int kMinimumAlignment = 16;
   ASSERT(Utils::IsPowerOfTwo(alignment));
   ASSERT(alignment >= kMinimumAlignment);
-  void* p = NULL;
-  int r;
-  r = posix_memalign(&p, alignment, size);
-  if (p == NULL) {
-    UNREACHABLE();
-  }
-  return p;
+  // Temporary workaround until xcode is upgraded.
+  // Mac guarantees malloc returns a 16 byte aligned memory chunk.
+  // Currently we only allocate with 16-bye alignment.
+  ASSERT(alignment == 16);
+  // TODO(johnmccutchan): Remove hack and switch to posix_memalign.
+  return malloc(size);
 }
 
 
 void OS::AlignedFree(void* ptr) {
   free(ptr);
 }
 
 
 word OS::ActivationFrameAlignment() {
   // OS X activation frames must be 16 byte-aligned; see "Mac OS X ABI
@@ skipping 108 matching lines @@
 void OS::Abort() {
   abort();
 }
 
 
 void OS::Exit(int code) {
   exit(code);
 }
 
 }  // namespace dart