Modules: follow up to r276769.

In r276769, I forgot to forward the driver option, add that here.

rdar://26675801


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@276797 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Driver/Tools.cpp b/lib/Driver/Tools.cpp
index 6c303b4..c5729ca 100644
--- a/lib/Driver/Tools.cpp
+++ b/lib/Driver/Tools.cpp
@@ -5019,6 +5019,7 @@
   }
 
   Args.AddLastArg(CmdArgs, options::OPT_fmodules_validate_system_headers);
+  Args.AddLastArg(CmdArgs, options::OPT_fmodules_disable_diagnostic_validation);
 
   // -faccess-control is default.
   if (Args.hasFlag(options::OPT_fno_access_control,