Closes #22258: Fix the the internal function set_inheritable() on Illumos.
This platform exposes the function ioctl(FIOCLEX), but calling it fails with
errno is ENOTTY: "Inappropriate ioctl for device". set_inheritable() now falls
back to the slower fcntl() (F_GETFD and then F_SETFD).
(Merge 3.4) Closes #22258: Fix the the internal function set_inheritable() on
Illumos.  This platform exposes the function ioctl(FIOCLEX), but calling it
fails with errno is ENOTTY: "Inappropriate ioctl for device". set_inheritable()
now falls back to the slower fcntl() (F_GETFD and then F_SETFD).