I made a look at this and it seems it can not do that without downloading opensans font source and putting it there.
در چهارشنبه, اوت 30 2023 at ۱۵:۱۵:۴۴ +02:00:00, Bastian Germann <bage@debian.org> نوشته بود:
Please check the latest git commit where I have demonstrated
that you can at least run parts of the build.
You should investigate how to call fontforge to build the ttf files.