Flatpak version attempts to use powerline
Running the flatpak version of builder on a system configured to use powerline makes the builder terminal try to use powerline, however the runtime doesn't have powerline installed. As a result the arrows don't show, as in #404 (closed). This is a duplicate of #404 (closed), but I don't know if I can reopen it.
I don't know if you want to move this issue upstream to the runtime maintainers or include powerline in the manifest here, so opening this to keep track.