HPCC-11851 Roxie index creation failing

Signed-off-by: Richard Chapman <rchapman@hpccsystems.com>
Merge pull request #6190 from richardkchapman/roxie-index-write

HPCC-11851 Roxie index creation failing

Reviewed-by: Gavin Halliday <ghalliday@hpccsystems.com>