fix `#load_directory` including nested directories

src/check_builtin.cpp

@@ -1533,6 +1533,10 @@ gb_internal LoadDirectiveResult check_load_directory_directive(CheckerContext *c
 
 		for (FileInfo fi : list) {
 			LoadFileCache *cache = nullptr;
+			if (fi.is_dir) {
+				continue;
+			}
+
 			if (cache_load_file_directive(c, call, fi.fullpath, err_on_not_found, &cache, LoadFileTier_Contents, /*use_mutex*/false)) {
 				array_add(&file_caches, cache);
 			} else {