flatc does not support output to stdout

[pablo-odorico]

It would be great if flatc had an option to output to stdout (e.g. -o -).

This would help when integrating it into a microservice that needs to convert files from .bin to .json, to avoid writing an extra temporary file to the file system.

Inputting from stdin would be less useful IMO, because in this case there's multiple files being read (.fbs + .bin) and because it's likely those input files already exist in the filesystem.