[llvm-readobj] Use stderr and not stdout for error messages.

llvm-svn: 256347
diff --git a/llvm/tools/llvm-readobj/llvm-readobj.cpp b/llvm/tools/llvm-readobj/llvm-readobj.cpp
index 92ee299..fa8fee2 100644
--- a/llvm/tools/llvm-readobj/llvm-readobj.cpp
+++ b/llvm/tools/llvm-readobj/llvm-readobj.cpp
@@ -232,8 +232,8 @@
 namespace llvm {
 
 LLVM_ATTRIBUTE_NORETURN void reportError(Twine Msg) {
-  outs() << "\nError reading file: " << Msg << ".\n";
-  outs().flush();
+  errs() << "\nError reading file: " << Msg << ".\n";
+  errs().flush();
   exit(1);
 }