VM: Support bootstrapping core libraries from Kernel binaries instead of source.

runtime/vm/kernel_binary.cc

Index: runtime/vm/kernel_binary.cc
diff --git a/runtime/vm/kernel_binary.cc b/runtime/vm/kernel_binary.cc
index aaf333358dab81b19c79db552e5525212c70ab3b..350690d6b474d252ce97590143f3066a0ecbae9f 100644
--- a/runtime/vm/kernel_binary.cc
+++ b/runtime/vm/kernel_binary.cc
@@ -1,6 +1,7 @@
 // Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
 // 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.
+#if !defined(DART_PRECOMPILED_RUNTIME)
 
 #include <map>
 #include <vector>
@@ -2901,3 +2902,4 @@ void WritePrecompiledKernel(ByteWriter* byte_writer, kernel::Program* program) {
 
 
 }  // namespace dart
+#endif  // !defined(DART_PRECOMPILED_RUNTIME)