[clang] Add a TODO for output paths in invocation path visitation (#167983)

Pointed out in code review downstream:
https://github.com/swiftlang/llvm-project/pull/11816

clang/lib/Frontend/CompilerInvocation.cpp

@@ -5322,6 +5322,7 @@ void CompilerInvocationBase::visitPathsImpl(
 
     RETURN_IF(Input.File);
   }
+  // TODO: Also report output files such as FrontendOpts.OutputFile;
   RETURN_IF(FrontendOpts.CodeCompletionAt.FileName);
   RETURN_IF_MANY(FrontendOpts.ModuleMapFiles);
   RETURN_IF_MANY(FrontendOpts.ModuleFiles);