Fix config value used for apcu-autoloader in dump-autoload command, fixes #6237

src/Composer/Command/DumpAutoloadCommand.php

@@ -57,7 +57,7 @@ EOT
 
         $optimize = $input->getOption('optimize') || $config->get('optimize-autoloader');
         $authoritative = $input->getOption('classmap-authoritative') || $config->get('classmap-authoritative');
-        $apcu = $input->getOption('apcu') || $config->get('apcu');
+        $apcu = $input->getOption('apcu') || $config->get('apcu-autoloader');
 
         if ($optimize || $authoritative) {
             $this->getIO()->writeError('<info>Generating optimized autoload files</info>');