Small const-correctness fix

llvm-svn: 50723
diff --git a/llvm/tools/llvmc2/Action.cpp b/llvm/tools/llvmc2/Action.cpp
index 82a1e0c..8d34910 100644
--- a/llvm/tools/llvmc2/Action.cpp
+++ b/llvm/tools/llvmc2/Action.cpp
@@ -48,7 +48,7 @@
   }
 }
 
-int llvmcc::Action::Execute() {
+int llvmcc::Action::Execute() const {
   if (VerboseMode) {
     std::cerr << Command_ << " ";
     std::for_each(Args_.begin(), Args_.end(), print_string);