Fix blackbox test discovery (#3099)
Fix blackbox test discovery (#3099)

Signed-off-by: Nathan Rebours <9d1531e67b3fd717aeb3bdeb8fe4128d946e28e7@gmail.com>
janestreet/jbuilder,janestreet/jbuilder,dra27/jbuilder,janestreet/jbuilder,dra27/jbuilder,dra27/jbuilder,janestreet/jbuilder,dra27/jbuilder,janestreet/jbuilder,dra27/jbuilder,dra27/jbuilder,janestreet/jbuilder