jpegexiforient silently does nothing on files that don't contain exif
tags. I'd be great if it could create them when called in set mode. (But
if it is a deliberate decision not to do so, at least it should inform
about the failure, and maybe give hints.)

I reported this bug at libjpeg-turbo upstream on github [1] but it seems
to be the wrong place. As it is unclear to me where the code is actually
coming from *, I am reporting here so that it can be forwarded to the
appropriate upstream project.
(* btw, libjpeg-turbo-progs's `Homepage` field seems to be wrong, then.)

Thanks,
Marian

[1] https://github.com/libjpeg-turbo/libjpeg-turbo/issues/494