Allow referencing scripts to extends @composer

src/Composer/EventDispatcher/EventDispatcher.php

@@ -173,7 +173,7 @@ class EventDispatcher
                 $args = array_merge($script, $event->getArguments());
                 $flags = $event->getFlags();
                 if (substr($callable, 0, 10) === '@composer ') {
-                    $exec = $this->getPhpExecCommand() . ' ' . ProcessExecutor::escape(getenv('COMPOSER_BINARY')) . substr($callable, 9);
+                    $exec = $this->getPhpExecCommand() . ' ' . ProcessExecutor::escape(getenv('COMPOSER_BINARY')) . ' ' . implode(' ', $args);
                     if (0 !== ($exitCode = $this->process->execute($exec))) {
                         $this->io->writeError(sprintf('<error>Script %s handling the %s event returned with error code '.$exitCode.'</error>', $callable, $event->getName()), true, IOInterface::QUIET);