[llvm-ar] errors go on stderr and not on stdout.

llvm-svn: 299548
diff --git a/llvm/tools/llvm-ar/llvm-ar.cpp b/llvm/tools/llvm-ar/llvm-ar.cpp
index 17e78a6b..23e86f0 100644
--- a/llvm/tools/llvm-ar/llvm-ar.cpp
+++ b/llvm/tools/llvm-ar/llvm-ar.cpp
@@ -52,7 +52,7 @@
 
 // Show the error message and exit.
 LLVM_ATTRIBUTE_NORETURN static void fail(Twine Error) {
-  outs() << ToolName << ": " << Error << ".\n";
+  errs() << ToolName << ": " << Error << ".\n";
   exit(1);
 }