Don't assume we want the iOS ABI if running simarm on Mac and the EABI otherwise.

runtime/platform/globals.h

Index: runtime/platform/globals.h
diff --git a/runtime/platform/globals.h b/runtime/platform/globals.h
index 7d5b431944935284486adf05174f01229c9dcd27..e3d1a340b4b7e35949e68d7e36c1b1ababf8d1a0 100644
--- a/runtime/platform/globals.h
+++ b/runtime/platform/globals.h
@@ -2,8 +2,8 @@
 // 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.
 
-#ifndef RUNTIME_PLATFORM_GLOBALS_H_
-#define RUNTIME_PLATFORM_GLOBALS_H_
+#ifndef PLATFORM_GLOBALS_H_
+#define PLATFORM_GLOBALS_H_
 
 // __STDC_FORMAT_MACROS has to be defined before including <inttypes.h> to
 // enable platform independent printf format specifiers.
@@ -365,6 +365,20 @@ typedef simd128_value_t fpu_register_t;
 #define ARCH_IS_MULTI_CORE 1
 #endif
 
+
+#if defined(TARGET_ARCH_ARM)
+#if defined(TARGET_ABI_IOS) && defined(TARGET_ABI_EABI)
+#error Both TARGET_ABI_IOS and TARGET_ABI_EABI defined.
+#elif !defined(TARGET_ABI_IOS) && !defined(TARGET_ABI_EABI)
+#if defined(TARGET_OS_MAC)
+#define TARGET_ABI_IOS 1
+#else
+#define TARGET_ABI_EABI 1
+#endif
+#endif
+#endif  // TARGET_ARCH_ARM
+
+
 // Short form printf format specifiers
 #define Pd PRIdPTR
 #define Pu PRIuPTR
@@ -683,4 +697,4 @@ static inline T ReadUnaligned(const T* ptr) {
 
 }  // namespace dart
 
-#endif  // RUNTIME_PLATFORM_GLOBALS_H_
+#endif  // PLATFORM_GLOBALS_H_