Add -lstdc++ to DragonFly tools.
Patch by Sascha Wildner.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@108830 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Driver/Tools.cpp b/lib/Driver/Tools.cpp
index 9bf17e6..6d13594 100644
--- a/lib/Driver/Tools.cpp
+++ b/lib/Driver/Tools.cpp
@@ -3298,6 +3298,11 @@
       CmdArgs.push_back("/usr/lib");
     }
 
+    if (D.CCCIsCXX) {
+      CmdArgs.push_back("-lstdc++");
+      CmdArgs.push_back("-lm");
+    }
+
     if (Args.hasArg(options::OPT_shared)) {
       CmdArgs.push_back("-lgcc_pic");
     } else {