Convert __thread_local_data to the singleton pattern

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@116500 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/src/condition_variable.cpp b/src/condition_variable.cpp
index 3bafa8c..6727a02 100644
--- a/src/condition_variable.cpp
+++ b/src/condition_variable.cpp
@@ -64,7 +64,7 @@
 void
 notify_all_at_thread_exit(condition_variable& cond, unique_lock<mutex> lk)
 {
-    __thread_local_data->notify_all_at_thread_exit(&cond, lk.release());
+    __thread_local_data()->notify_all_at_thread_exit(&cond, lk.release());
 }
 
 _LIBCPP_END_NAMESPACE_STD