Collect a prebuilt board-agnostic root filesystem tarball and a prebuilt PYNQ source distribution. Starting in PYNQ v3.0, by default the SD card build flow expects a prebuilt root filesystem and a PYNQ source distribution to speedup and simplify user rebuilds of SD card images. These binaries can be found at [the PYNQ boards page](http://www.pynq.io/board.html/) and copied into the sdbuild prebuilt folder
I could only find the rootfs’s in the pynq boards page