minor #17401 [2.7] Use is_subclass_of instead of reflection (Ener-Getick)

This PR was merged into the 2.7 branch.

Discussion
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[2.7] Use is_subclass_of instead of reflection

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets |
| License       | MIT

Follows symfony/symfony#17400

>
For performance reason, I replaced a reflection instantiation by ``is_subclass_of``.

Commits
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5af5d06 Use is_subclass_of instead of reflection

Author: fabpot

DependencyInjection/Compiler/AddConsoleCommandPass.php

@@ -37,8 +37,7 @@ public function process(ContainerBuilder $container)
             }
 
             $class = $container->getParameterBag()->resolveValue($definition->getClass());
-            $r = new \ReflectionClass($class);
-            if (!$r->isSubclassOf('Symfony\\Component\\Console\\Command\\Command')) {
+            if (!is_subclass_of($class, 'Symfony\\Component\\Console\\Command\\Command')) {
                 throw new \InvalidArgumentException(sprintf('The service "%s" tagged "console.command" must be a subclass of "Symfony\\Component\\Console\\Command\\Command".', $id));
             }
             $container->setAlias('console.command.'.strtolower(str_replace('\\', '_', $class)), $id);