Fix -pthread on dragonfly.  Patch by Sascha Wildner.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@85679 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Driver/Tools.cpp b/lib/Driver/Tools.cpp
index b29265b..47234ef 100644
--- a/lib/Driver/Tools.cpp
+++ b/lib/Driver/Tools.cpp
@@ -2710,7 +2710,7 @@
 
 
     if (Args.hasArg(options::OPT_pthread))
-      CmdArgs.push_back("-lthread_xu");
+      CmdArgs.push_back("-lpthread");
 
     if (!Args.hasArg(options::OPT_nolibc)) {
       CmdArgs.push_back("-lc");