Fix arch_helper() to return the list of supported architectures.

llvm-svn: 157643
diff --git a/lldb/source/Interpreter/CommandObject.cpp b/lldb/source/Interpreter/CommandObject.cpp
index af9aa39..dbbd093 100644
--- a/lldb/source/Interpreter/CommandObject.cpp
+++ b/lldb/source/Interpreter/CommandObject.cpp
@@ -850,12 +850,12 @@
 const char *arch_helper()
 {
     static StreamString g_archs_help;
-    if (g_archs_help.GetData() == NULL)
+    if (g_archs_help.Empty())
     {
         StringList archs;
         ArchSpec::AutoComplete(NULL, archs);
         g_archs_help.Printf("These are the supported architecture names:\n");
-        archs.Join("%s\n", g_archs_help);
+        archs.Join("\n", g_archs_help);
     }
     return g_archs_help.GetData();
 }