Disable the weak persistent handle test on non-ia32 targets.

runtime/vm/dart_api_impl_test.cc

Index: runtime/vm/dart_api_impl_test.cc
diff --git a/runtime/vm/dart_api_impl_test.cc b/runtime/vm/dart_api_impl_test.cc
index d65c7a89e21f75922b1cccbdb3e23a5dc8c6cdcd..b0f75016350bef146b3133e9e64f566d9c678e25 100644
--- a/runtime/vm/dart_api_impl_test.cc
+++ b/runtime/vm/dart_api_impl_test.cc
@@ -764,6 +764,8 @@ UNIT_TEST_CASE(NewPersistentHandle_FromPersistentHandle) {
 }
 
 
+#if defined(TARGET_ARCH_IA32)  // only ia32 can run execution tests.
+
 TEST_CASE(WeakPersistentHandle) {
   Dart_Handle weak_new_ref = Dart_Null();
   EXPECT(Dart_IsNull(weak_new_ref));
@@ -865,6 +867,8 @@ TEST_CASE(WeakPersistentHandle) {
   EXPECT(Dart_IsNull(weak_old_ref));
 }
 
+#endif
+
 
 // Unit test for creating multiple scopes and local handles within them.
 // Ensure that the local handles get all cleaned out when exiting the