[llvm-readobj] Fix output interleaving issue caused by using multiple streams at the same time.

Summary:
Use llvm::fouts() as the default stream for outputing. No new stream
should be constructed to output at the same time.

https://bugs.llvm.org/show_bug.cgi?id=42140

Reviewers: jhenderson, grimar, MaskRay, phosek, rupprecht

Reviewed By: rupprecht

Subscribers: llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D63115

Patch by Yuanfang Chen!

llvm-svn: 363198
diff --git a/llvm/tools/llvm-readobj/MachODumper.cpp b/llvm/tools/llvm-readobj/MachODumper.cpp
index 5149f46..32a3866 100644
--- a/llvm/tools/llvm-readobj/MachODumper.cpp
+++ b/llvm/tools/llvm-readobj/MachODumper.cpp
@@ -689,7 +689,7 @@
   llvm::stable_sort(Libs);
 
   for (const auto &L : Libs) {
-    outs() << "  " << L << "\n";
+    W.startLine() << L << "\n";
   }
 }