fix custom filename for tmp file

Author: phpdevcommunity

src/TempFile.php

@@ -78,7 +78,10 @@ public static function createTempFile(?string $filename = null): FileInfo
         if ($filename === null) {
             $filename = tempnam(sys_get_temp_dir(), 'tmp_');
         } else {
-            $filename = sys_get_temp_dir() . DIRECTORY_SEPARATOR . $filename;
+
+            if ($filename[0] !== '/') {
+                $filename = sys_get_temp_dir() . DIRECTORY_SEPARATOR . $filename;
+            }
             if (!file_exists($filename)) {
                 touch($filename);
             }