Add a snapshot of flutter/engine/src/build to our sdk

build/config/ios/XcodeHarness/FakeMain.m

Index: build/config/ios/XcodeHarness/FakeMain.m
diff --git a/build/config/ios/XcodeHarness/FakeMain.m b/build/config/ios/XcodeHarness/FakeMain.m
new file mode 100644
index 0000000000000000000000000000000000000000..5ddbd34dc185599e6f86f1cd74f912ec62cdd7da
--- /dev/null
+++ b/build/config/ios/XcodeHarness/FakeMain.m
@@ -0,0 +1,10 @@
+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#import <Foundation/Foundation.h>
+
+int main(int argc, char* argv[]) {
+  NSCAssert(NO, @"Placeholder for Xcode. Should never be run");
+  return EXIT_FAILURE;
+}