Update GenerateSitemap.php

used the Magento methods to check if a directory exists/create a directory

Cron/GenerateSitemap.php

@@ -16,6 +16,8 @@
 use Vendic\VueStorefrontSitemap\Model\Configuration;
 use Vendic\VueStorefrontSitemap\Model\ProductCollection;
 use Vendic\VueStorefrontSitemap\Model\SitemapFactory;
+use Magento\Framework\Filesystem\Driver\File;
+use Magento\Framework\Filesystem\Io\File as Io;
 
 class GenerateSitemap
 {
@@ -45,19 +47,32 @@ class GenerateSitemap
      * @var CategoryCollection
      */
     protected $categoryCollection;
+    /**
+     * @var File
+     */
+    protected $fileDriver;
+    /**
+     * @var Io
+     */
+    protected $io;
 
     public function __construct(
         CategoryCollection $categoryCollection,
         Configuration $configuration,
         ProductCollection $productCollection,
         DirectoryList $directoryList,
-        SitemapFactory $sitemapFactory
+        SitemapFactory $sitemapFactory,
+        File $fileDriver,
+        Io $io
     ) {
         $this->directoryList = $directoryList;
         $this->sitemapFactory = $sitemapFactory;
         $this->productCollection = $productCollection;
         $this->configuration = $configuration;
         $this->categoryCollection = $categoryCollection;
+        $this->fileDriver = $fileDriver;
+        $this->io = $io;
+
     }
 
     public function execute() : void
@@ -67,9 +82,7 @@ public function execute() : void
         $path = $this->getPubPath();
 
         // Create directory at Path if doesn't exists
-        if (!file_exists($path)) {
-            mkdir($path, 0777, true);
-        }
+        if (!$this->fileDriver->isExists($path)) $this->io->mkdir($path, 0775);
 
         // Sitemap configuration
         $this->sitemap = $this->sitemapFactory->create($domain);