Add exitCode setter to set the exit code returned by the Dart VM

runtime/bin/builtin_natives.cc

Index: runtime/bin/builtin_natives.cc
diff --git a/runtime/bin/builtin_natives.cc b/runtime/bin/builtin_natives.cc
index 8fedb2dd2420c797e649fff5563da3c1f6353c44..159cf25806a3ef121a23c6777b55df372ba3fe9e 100644
--- a/runtime/bin/builtin_natives.cc
+++ b/runtime/bin/builtin_natives.cc
@@ -24,7 +24,6 @@
   V(Directory_Delete, 2)                                                       \
   V(Directory_Rename, 2)                                                       \
   V(Directory_NewServicePort, 0)                                               \
-  V(Exit, 1)                                                                   \
   V(File_Open, 2)                                                              \
   V(File_Exists, 1)                                                            \
   V(File_Close, 1)                                                             \
@@ -104,13 +103,3 @@ void FUNCTION_NAME(Logger_PrintString)(Dart_NativeArguments args) {
   Builtin::PrintString(stdout, Dart_GetNativeArgument(args, 0));
   Dart_ExitScope();
 }
-
-
-void FUNCTION_NAME(Exit)(Dart_NativeArguments args) {
-  Dart_EnterScope();
-  int64_t status = 0;
-  // Ignore result if passing invalid argument and just exit 0.
-  DartUtils::GetInt64Value(Dart_GetNativeArgument(args, 0), &status);
-  Dart_ExitScope();
-  exit(static_cast<int>(status));
-}