Add index with distributed local sort does not trigger import

[tangenta]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

set global tidb_enable_dist_task = on;
set global tidb_cloud_storage_uri = '';

Add index on a large table.

2. What did you expect to see? (Required)

No error.

3. What did you see instead (Required)

error="write /var/lib/tidb/data-0/tmp_ddl-4000/109/b8f3741c-2a87-5acf-944a-62ce994e2136.sst/535dcafe-9b06-452c-a65b-f28d686397f7.sst: no space left on device"

4. What is your TiDB version? (Required)

6660de7