Return correct ActivationFrameAlignment for iOS simulator variants

runtime/vm/os_macos.cc

Index: runtime/vm/os_macos.cc
diff --git a/runtime/vm/os_macos.cc b/runtime/vm/os_macos.cc
index a7d3ee672364ef5fedf66fbb956ddf1a5bd1e546..1a9537e82bd8d92fa2c6f41364c63994213172bb 100644
--- a/runtime/vm/os_macos.cc
+++ b/runtime/vm/os_macos.cc
@@ -149,6 +149,10 @@ intptr_t OS::ActivationFrameAlignment() {
   return 8;
 #elif TARGET_ARCH_ARM64
   return 16;
+#else

[rmacnak, 2015/11/03 21:13:00]

Let's avoid fall through.

#elif TARGET_ARCH_IA32
  return 16;  // iOS simulator
#elif TARGET_ARCH_X64
  return 16;  // iOS simulator
#else
#error Unimplemented

+  // If the target is iOS but arch not one of ARM or ARM64, this is a simulator
+  // build
+  return 16;
 #endif
 #else  // TARGET_OS_IOS
   // OS X activation frames must be 16 byte-aligned; see "Mac OS X ABI