Apply the "purity" patch (updated for 5.4.2).

--- a/lib/Driver/ToolChains/Gnu.cpp
+++ b/lib/Driver/ToolChains/Gnu.cpp
@@ -488,11 +488,5 @@
     if (Args.hasArg(options::OPT_rdynamic))
       CmdArgs.push_back("-export-dynamic");
-
-    if (!Args.hasArg(options::OPT_shared) && !IsStaticPIE) {
-      CmdArgs.push_back("-dynamic-linker");
-      CmdArgs.push_back(Args.MakeArgString(Twine(D.DyldPrefix) +
-                                           ToolChain.getDynamicLinker(Args)));
-    }
   }

   CmdArgs.push_back("-o");