[Support] Make error banner optional in logAllUnhandledErrors

In a lot of places an empty string was passed as the ErrorBanner to
logAllUnhandledErrors. This patch makes that argument optional to
simplify the call sites.

llvm-svn: 346604
diff --git a/llvm/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldMachO.cpp b/llvm/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldMachO.cpp
index c5a215c..d47fcd4 100644
--- a/llvm/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldMachO.cpp
+++ b/llvm/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldMachO.cpp
@@ -370,7 +370,7 @@
   else {
     HasError = true;
     raw_string_ostream ErrStream(ErrorStr);
-    logAllUnhandledErrors(ObjSectionToIDOrErr.takeError(), ErrStream, "");
+    logAllUnhandledErrors(ObjSectionToIDOrErr.takeError(), ErrStream);
     return nullptr;
   }
 }