`O_TMPFILE` requires file system support, which may not be available in
certain environments, usually containerized ones. So do not use it.
A new function is added for tests to be able to create unnamed temporary
files using `libcamera::MemFd` as the implementation.
Signed-off-by: Barnabás Pőcze <barnabas.pocze@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Paul Elder <paul.elder@ideasonboard.com>
b181327131