manifest: Add jhbuild to -devel set
manifest: Add jhbuild to -devel set

It's useful for developers.

GNOME/gnome-ostree,vrutkovs/vrutkovs.github.io,vrutkovs/vrutkovs.github.io,chergert/gnome-continuous,GNOME/gnome-ostree,vrutkovs/vrutkovs.github.io,chergert/gnome-continuous,chergert/gnome-continuous,GNOME/gnome-ostree