graphics/openimageio: Prep for GCC 7
graphics/openimageio: Prep for GCC 7

Signed-off-by: Christoph Willing <1757c047fc1eb5ae34b544946e318f58134b07c6@linux.com>

panosmdma/SlackOnly-SlackBuilds,panosmdma/SlackOnly-SlackBuilds,panosmdma/SlackOnly-SlackBuilds,panosmdma/SlackOnly-SlackBuilds,panosmdma/SlackOnly-SlackBuilds,panosmdma/SlackOnly-SlackBuilds,panosmdma/SlackOnly-SlackBuilds