Make llvm-nm return 1 on error.

This is a small compatibility improvement with gnu nm and makes llvm-nm more
useful as a testing tool.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@185546 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/tools/llvm-nm/llvm-nm.cpp b/tools/llvm-nm/llvm-nm.cpp
index cb46520..c33289b 100644
--- a/tools/llvm-nm/llvm-nm.cpp
+++ b/tools/llvm-nm/llvm-nm.cpp
@@ -121,6 +121,8 @@
 
   bool MultipleFiles = false;
 
+  bool HadError = false;
+
   std::string ToolName;
 }
 
@@ -132,6 +134,7 @@
 static bool error(error_code ec, Twine path = Twine()) {
   if (ec) {
     error(ec.message(), path);
+    HadError = true;
     return true;
   }
   return false;
@@ -429,6 +432,7 @@
   } else {
     errs() << ToolName << ": " << Filename << ": "
            << "unrecognizable file type\n";
+    HadError = true;
     return;
   }
 }
@@ -463,5 +467,9 @@
 
   std::for_each(InputFilenames.begin(), InputFilenames.end(),
                 DumpSymbolNamesFromFile);
+
+  if (HadError)
+    return 1;
+
   return 0;
 }