HPCC-12420 OSX eclcc stdout/stderr pipes get closed prematurely

Combination of recursive call (DBGLOG) and unexpected response from ioctl on OSX.

Fixes HPCC-12420

Signed-off-by: Gordon Smith <gordonjsmith@gmail.com>
Merge pull request #6539 from GordonSmith/HPCC-12420

HPCC-12420 OSX eclcc stdout/stderr pipes get closed prematurely

Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>