Index: lib/Frontend/HeaderIncludeGen.cpp
===================================================================
--- lib/Frontend/HeaderIncludeGen.cpp
+++ lib/Frontend/HeaderIncludeGen.cpp
@@ -131,5 +131,6 @@
     Msg += '\n';
 
     OutputFile->write(Msg.data(), Msg.size());
+    OutputFile->flush();
   }
 }