Propogate the error message, not just the error state.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@128094 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/ExecutionEngine/RuntimeDyld.h

@@ -38,6 +38,7 @@ public:
   // FIXME: Should be parameterized to get the memory block associated with
   // a particular loaded object.
   sys::MemoryBlock getMemoryBlock();
+  StringRef getErrorString();
 };
 
 } // end namespace llvm