Add a little hack to emulate a clang crash, so the diagnostics generator can be
tested.

llvm-svn: 155205
diff --git a/clang/lib/Driver/Driver.cpp b/clang/lib/Driver/Driver.cpp
index 1ffa9b7..0d105ac 100644
--- a/clang/lib/Driver/Driver.cpp
+++ b/clang/lib/Driver/Driver.cpp
@@ -379,7 +379,7 @@
     return;  
 
   // Don't try to generate diagnostics for link jobs.
-  if (FailingCommand->getCreator().isLinkJob())
+  if (FailingCommand && FailingCommand->getCreator().isLinkJob())
     return;
 
   Diag(clang::diag::note_drv_command_failed_diag_msg)