Add -add-plugin flag, which runs plugins in addition to codegen.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@124227 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/clang/Driver/CC1Options.td b/include/clang/Driver/CC1Options.td
index 58353f1..d36e45d 100644
--- a/include/clang/Driver/CC1Options.td
+++ b/include/clang/Driver/CC1Options.td
@@ -290,10 +290,12 @@
 def load : Separate<"-load">, MetaVarName<"<dsopath>">,
   HelpText<"Load the named plugin (dynamic shared object)">;
 def plugin : Separate<"-plugin">, MetaVarName<"<name>">,
-  HelpText<"Use the named plugin action (use \"help\" to list available options)">;
+  HelpText<"Use the named plugin action instead of the default action (use \"help\" to list available options)">;
 def plugin_arg : JoinedAndSeparate<"-plugin-arg-">,
     MetaVarName<"<name> <arg>">,
     HelpText<"Pass <arg> to plugin <name>">;
+def add_plugin : Separate<"-add-plugin">, MetaVarName<"<name>">,
+  HelpText<"Use the named plugin action in addition to the default action">;
 def resource_dir : Separate<"-resource-dir">,
   HelpText<"The directory which holds the compiler resource files">;
 def version : Flag<"-version">,