Add support to Darwin for the -export_dynamic' flag to the linker.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@169775 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Driver/Tools.cpp b/lib/Driver/Tools.cpp
index 634e020..2872749 100644
--- a/lib/Driver/Tools.cpp
+++ b/lib/Driver/Tools.cpp
@@ -4115,6 +4115,9 @@
   if (Args.hasArg(options::OPT_ObjC) || Args.hasArg(options::OPT_ObjCXX))
     CmdArgs.push_back("-ObjC");
 
+  if (Args.hasArg(options::OPT_rdynamic))
+    CmdArgs.push_back("-export_dynamic");
+
   CmdArgs.push_back("-o");
   CmdArgs.push_back(Output.getFilename());