[llvm-dlltool] Mention arm64 in the lists of architecture alternatives

[mstorsjo]

Summary

This was missed in SVN r310223 when arm64 support was added.

[ruiu]

LGTM

lib/ToolDrivers/llvm-dlltool/DlltoolDriver.cpp

if (MissingCount) {
     llvm::errs() << Args.getArgString(MissingIndex) << ": missing argument\n";
     return 1;
   }
 
   // Handle when no input or output is specified
   if (Args.hasArgNoClaim(OPT_INPUT) ||
       (!Args.hasArgNoClaim(OPT_d) && !Args.hasArgNoClaim(OPT_l))) {
     Table.PrintHelp(outs(), ArgsArr[0], "dlltool", false);
-    llvm::outs() << "\nTARGETS: i386, i386:x86-64, arm\n";
+    llvm::outs() << "\nTARGETS: i386, i386:x86-64, arm, arm64\n";
     return 1;
   }
 
   if (!Args.hasArgNoClaim(OPT_m) && Args.hasArgNoClaim(OPT_d)) {
     llvm::errs() << "error: no target machine specified\n"
-                 << "supported targets: i386, i386:x86-64, arm\n";
+                 << "supported targets: i386, i386:x86-64, arm, arm64\n";
     return 1;
   }
 
   for (auto *Arg : Args.filtered(OPT_UNKNOWN))
     llvm::errs() << "ignoring unknown argument: " << Arg->getSpelling() << "\n";
 
   if (!Args.hasArg(OPT_d)) {
     llvm::errs() << "no definition file specified\n";