Fix the SubCommands find_if return type.

Author: Prabhuk

llvm/lib/Option/OptTable.cpp

@@ -756,11 +756,12 @@ void OptTable::internalPrintHelp(
   // pairs.
   std::map<std::string, std::vector<OptionInfo>> GroupedOptionHelp;
 
-  const auto ActiveSubCommand =
+  typename ArrayRef<OptTable::SubCommand>::iterator ActiveSubCommand =
       std::find_if(SubCommands.begin(), SubCommands.end(),
                    [&](const auto &C) { return SubCommand == C.Name; });
   if (!SubCommand.empty()) {
-    assert(ActiveSubCommand != nullptr && "Not a valid registered subcommand.");
+    assert(ActiveSubCommand != SubCommands.end() &&
+           "Not a valid registered subcommand.");
     OS << ActiveSubCommand->HelpText << "\n\n";
     if (!StringRef(ActiveSubCommand->Usage).empty())
       OS << "USAGE: " << ActiveSubCommand->Usage << "\n\n";