umask-util: add helper that resets umask until end of current code block

src/test/test-fs-util.c

@@ -765,7 +765,6 @@ static void test_rename_noreplace(void) {
 
 static void test_chmod_and_chown(void) {
         _cleanup_(rm_rf_physical_and_freep) char *d = NULL;
-        _unused_ _cleanup_umask_ mode_t u = umask(0000);
         struct stat st;
         const char *p;
 
@@ -774,6 +773,8 @@ static void test_chmod_and_chown(void) {
 
         log_info("/* %s */", __func__);
 
+        BLOCK_WITH_UMASK(0000);
+
         assert_se(mkdtemp_malloc(NULL, &d) >= 0);
 
         p = strjoina(d, "/reg");