Support -rdynamic option in the new driver

lib/Driver/Tools.cpp

Index: lib/Driver/Tools.cpp
diff --git a/lib/Driver/Tools.cpp b/lib/Driver/Tools.cpp
index f4f7c4e1d36c937ab54a185d76b6fc53721683fb..6df472c336efb58c7d0436c518e6d170fb2f6182 100644
--- a/lib/Driver/Tools.cpp
+++ b/lib/Driver/Tools.cpp
@@ -8223,10 +8223,15 @@ void pnacltools::Link::ConstructJob(Compilation &C, const JobAction &JA,
     CmdArgs.push_back(Args.MakeArgString("--sysroot=" + D.SysRoot));
 
   if (Arg *A = Args.getLastArg(options::OPT_shared,
-                               options::OPT_dynamic,
-                               options::OPT_rdynamic))
+                               options::OPT_dynamic))
     D.Diag(diag::err_drv_unsupported_opt) << A->getOption().getName();
 
+  // This option does not currently have any effect for bitcode linking,
+  // but we support it for backwards compatibility with the legacy driver
+  // and existing software packages.
+  if (Args.hasArg(options::OPT_rdynamic))
+    CmdArgs.push_back("-export-dynamic");
+
   std::string TripleStr = ToolChain.ComputeEffectiveClangTriple(Args);
   if (ToolChain.getArch() != llvm::Triple::le32)
     D.Diag(diag::err_target_unsupported_arch) << ToolChain.getArchName()