Fix optimized_stacktrace_test with precompilation.

runtime/vm/code_generator.cc

Index: runtime/vm/code_generator.cc
diff --git a/runtime/vm/code_generator.cc b/runtime/vm/code_generator.cc
index 9a0d5f91e4267c23f09044541908888554b85b74..97013fb0c9ddc3f0ca8bfc4cae632487a8d2eeb1 100644
--- a/runtime/vm/code_generator.cc
+++ b/runtime/vm/code_generator.cc
@@ -1319,8 +1319,10 @@ DEFINE_RUNTIME_ENTRY(StackOverflow, 0) {
     intptr_t num_frames = stack->Length();
     for (intptr_t i = 0; i < num_frames; i++) {
       ActivationFrame* frame = stack->FrameAt(i);
+#ifndef DART_PRECOMPILED_RUNTIME
       // Ensure that we have unoptimized code.
       frame->function().EnsureHasCompiledUnoptimizedCode();
+#endif
       // Variable locations and number are unknown when precompiling.
       const int num_vars =
          FLAG_precompiled_runtime ? 0 : frame->NumLocalVariables();