“Why do programs I compile become all-zero files after rebooting?”

well, maybe that untested filesystem-related kernel patch you applied has something to do with it :D

But seriously, if anyone wants to make a very cursed unix system: apply this diff (note: old version by now) to FreeBSD from around now (say the beginning of 2020 — happy new year!), build programs using clang/lld 9.x and reboot.