llvmc: Add a new option type (switch_list).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@108673 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/CompilerDriver/Common.td

@@ -32,6 +32,7 @@ def actions;
 
 def alias_option;
 def switch_option;
+def switch_list_option;
 def parameter_option;
 def parameter_list_option;
 def prefix_option;