HPCC-9482 Fix code for calls to external c++ functions returning rows.

A regression from the time when we switched to linkcounted rows everywhere.

Signed-off-by: Gavin Halliday <gavin.halliday@lexisnexis.com>
HPCC-9482 Add compile time check for returning variable length rows

Signed-off-by: Gavin Halliday <gavin.halliday@lexisnexis.com>
Merge pull request #4494 from ghalliday/issue9482

HPCC-9482 Fix code for calls to external c++ functions returning rows.

Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>