WIP sstable: seal_sstable: link staging sstables to base dir

staging sstables need to be compacted as any other sstable.
In particular, they need to be subject to cleanup compaction
and scrubbing.

To achieve that, link them to the base dir when sealed.
When moved out of staging, table::move_sstables_from_staging
already unlinks the sstable from the staging subdirectory
if its get_dir() is set to the base dir.

Fix scylladb#9559

Signed-off-by: Benny Halevy <bhalevy@scylladb.com>

sstables/sstables.cc

@@ -939,6 +939,12 @@ future<> sstable::seal_sstable() {
     }
     // If this point was reached, sstable should be safe in disk.
     sstlog.debug("SSTable with generation {} of {}.{} was sealed successfully.", _generation, _schema->ks_name(), _schema->cf_name());
+    if (requires_view_building()) {
+        sstlog.debug("Linking {} to base directory", _generation, _schema->ks_name(), _schema->cf_name());
+        sstring base_dir = fs::path(_dir).parent_path().native();
+        co_await create_links(base_dir, _generation);
+        _dir = std::move(base_dir);
+    }
 }
 
 void sstable::write_crc(const checksum& c) {