BUGFIX: make prunner binary installer more robust

Author: skurfuerst

Classes/Composer/InstallerScripts.php

@@ -55,7 +55,7 @@ public static function postUpdateAndInstall(Event $event)
             echo '> Download complete.' . "\n";
 
             file_put_contents('Data/Temporary/prunner.tar.gz', $downloadedFileContents);
-            unlink('Data/Temporary/prunner.tar');
+            Files::unlink('Data/Temporary/prunner.tar');
 
             // decompress from gz
             $p = new PharData('Data/Temporary/prunner.tar.gz');