improve unlinking potential race condition

* fix rare race condition on file cache unlink
* remove unnecessary reset()
* improve code readability using variable

src/Psalm/Config.php

@@ -2296,20 +2296,29 @@ public static function removeCacheDirectory(string $dir): void
                     continue;
                 }
 
+                $full_path = $dir . '/' . $object;
+
                 // if it was deleted in the meantime/race condition with other psalm process
-                if (!file_exists($dir . '/' . $object)) {
+                if (!file_exists($full_path)) {
                     continue;
                 }
 
-                if (filetype($dir . '/' . $object) === 'dir') {
-                    self::removeCacheDirectory($dir . '/' . $object);
+                if (filetype($full_path) === 'dir') {
+                    self::removeCacheDirectory($full_path);
                 } else {
-                    unlink($dir . '/' . $object);
+                    try {
+                        unlink($full_path);
+                    } catch (RuntimeException $e) {
+                        clearstatcache(true, $full_path);
+                        if (file_exists($full_path)) {
+                            // rethrow the error with default message
+                            // it contains the reason why deletion failed
+                            throw $e;
+                        }
+                    }
                 }
             }
 
-            reset($objects);
-
             // may have been removed in the meantime
             clearstatcache(true, $dir);
             if (is_dir($dir)) {