Work around erroneous GCC report about potentially clobbered variable.

runtime/vm/flow_graph_inliner.cc

Index: runtime/vm/flow_graph_inliner.cc
diff --git a/runtime/vm/flow_graph_inliner.cc b/runtime/vm/flow_graph_inliner.cc
index 601c72dcbfb36e89fb0acf0d2bacd5b71f405527..1734ee1e62de6c04685f098f9d0c34fee976844f 100644
--- a/runtime/vm/flow_graph_inliner.cc
+++ b/runtime/vm/flow_graph_inliner.cc
@@ -648,7 +648,8 @@ class CallSiteInliner : public ValueObject {
 
     // Abort if this is a recursive occurrence.
     Definition* call = call_data->call;
-    const bool is_recursive_call = IsCallRecursive(unoptimized_code, call);
+    // Added 'volatile' works around a possible GCC 4.9 compiler bug.
+    volatile bool is_recursive_call = IsCallRecursive(unoptimized_code, call);
     if (is_recursive_call &&
         inlining_recursion_depth_ >= FLAG_inlining_recursion_depth_threshold) {
       TRACE_INLINING(OS::Print("     Bailout: recursive function\n"));