VM: Add dart_precompiled build target, a standalone VM without the JIT compiler.

runtime/vm/isolate.cc

Index: runtime/vm/isolate.cc
diff --git a/runtime/vm/isolate.cc b/runtime/vm/isolate.cc
index 6d201578f04cc8f730de93eb0c714d9937e34e97..e086d22516e8d3ae9e79992f0eae6ad1e2d2ab1c 100644
--- a/runtime/vm/isolate.cc
+++ b/runtime/vm/isolate.cc
@@ -1695,7 +1695,9 @@ void Isolate::LowLevelShutdown() {
 void Isolate::Shutdown() {
   ASSERT(this == Isolate::Current());
   // Wait until all background compilation has finished.
-  BackgroundCompiler::Stop(background_compiler_);
+  if (background_compiler_ != NULL) {
+    BackgroundCompiler::Stop(background_compiler_);
+  }
 
 #if defined(DEBUG)
   if (heap_ != NULL) {