[lldb/Driver] Error out when encountering unknown arguments

[JDevlieghere]

Summary

There appears to be consensus in D80165 that this is the desired behavior and I personally agree.

[labath]

yep

lldb/test/Shell/Driver/TestPositionalArgs.test

 
 RUN: %lldb -x -b %t.foo -- bar -baz --quux | FileCheck %s --check-prefix DASH
 RUN: %lldb -x -b -- %t.foo bar -baz --quux | FileCheck %s --check-prefix DASH
 RUN: %lldb -x -b -f %t.foo -- bar -baz --quux | FileCheck %s --check-prefix DASH
 
 DASH: Current executable set to {{.*}}foo
 DASH: target.run-args "bar" "-baz" "--quux"
 
-RUN: %lldb -x -b %t.foo bar -baz --quux 2>&1 | FileCheck %s --check-prefix UNKNOWN
-RUN: %lldb -x -b -f %t.foo bar -baz --quux 2>&1 | FileCheck %s --check-prefix UNKNOWN
+RUN: not %lldb -x -b %t.foo bar -baz --quux 2>&1 | FileCheck %s --check-prefix UNKNOWN
+RUN: not %lldb -x -b -f %t.foo bar -baz --quux 2>&1 | FileCheck %s --check-prefix UNKNOWN
 
-UNKNOWN: warning: ignoring unknown option: -baz
-UNKNOWN: warning: ignoring unknown option: --quux
-UNKNOWN: Current executable set to {{.*}}foo
-UNKNOWN: target.run-args "bar"
+UNKNOWN: error: unknown option: -baz
+UNKNOWN: error: unknown option: --quux

lldb/tools/driver/Driver.cpp

int main(int argc, char const *argv[]) {
   ArrayRef<const char *> arg_arr = makeArrayRef(argv + 1, argc - 1);
   opt::InputArgList input_args = T.ParseArgs(arg_arr, MAI, MAC);
 
   if (input_args.hasArg(OPT_help)) {
     printHelp(T, llvm::sys::path::filename(argv[0]));
     return 0;
   }
 
+  // Error out on unknown options.
+  if (input_args.hasArg(OPT_UNKNOWN)) {
     for (auto *arg : input_args.filtered(OPT_UNKNOWN)) {
-    WithColor::warning() << "ignoring unknown option: " << arg->getSpelling()
-                         << '\n';
+      WithColor::error() << "unknown option: " << arg->getSpelling() << '\n';
+    }
+    return 1;
   }
 
   if (auto exit_code = InitializeReproducer(input_args)) {
     return *exit_code;
   }
 
   // Register the reproducer signal handler.
   llvm::sys::AddSignalHandler(reproducer_handler, const_cast<char *>(argv[0]));