Validate options in test_old

Regularly try to use this one with --version instead of
--php-version, which fails in a non-obvious way.

test_old/run.php

@@ -26,6 +26,12 @@ function showHelp($error) {
  );
 }
 
+$allowedOptions = [
+ '--no-progress' => true,
+ '--verbose' => true,
+ '--php-version' => true,
+];
+
 $options = array();
 $arguments = array();
 
@@ -35,7 +41,11 @@ function showHelp($error) {
 foreach ($argv as $arg) {
  if ('-' === $arg[0]) {
  $parts = explode('=', $arg);
- $options[$parts[0]] = $parts[1] ?? true;
+ $name = $parts[0];
+ if (!isset($allowedOptions[$name])) {
+ showHelp("Unknown option \"$name\"");
+ }
+ $options[$name] = $parts[1] ?? true;
  } else {
  $arguments[] = $arg;
  }