Eliminate dependencies on assemblers and code stubs in precompiled runtime.

runtime/vm/block_scheduler.cc

Index: runtime/vm/block_scheduler.cc
diff --git a/runtime/vm/block_scheduler.cc b/runtime/vm/block_scheduler.cc
index 7411fccecea25cfb5cd9162b573c7d6a35ec9f5b..3f3c590058cd4b4fdf654aaf4996cd9d2ce2a29a 100644
--- a/runtime/vm/block_scheduler.cc
+++ b/runtime/vm/block_scheduler.cc
@@ -2,6 +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.
 
+#if !defined(DART_PRECOMPILED_RUNTIME)
+
 #include "vm/block_scheduler.h"
 
 #include "vm/allocation.h"
@@ -217,3 +219,5 @@ void BlockScheduler::ReorderBlocks() const {
 }
 
 }  // namespace dart
+
+#endif  // !defined(DART_PRECOMPILED_RUNTIME)