When building phar, unlink existing file only of it exists

build-phar.php

 <?php
 $pharName = 'cfgen.phar';
-unlink($pharName);
+if (file_exists($pharName)) {
+    unlink($pharName);
+}
 $p = new Phar($pharName, FilesystemIterator::CURRENT_AS_FILEINFO | FilesystemIterator::KEY_AS_FILENAME, $pharName);
 $p->startBuffering();
 $p->setStub("#!/usr/bin/env php\n<?php Phar::mapPhar(); include \"phar://$pharName/src/cfgen.php\"; __HALT_COMPILER(); ?>");