-d                       - Do not fork to background, debug mode

--mountdir [mount_dir]
-m [mount_dir]           - Path to a directory where the fileszstem will be mounted
                         - The directory must be empty, else it will refuse to mount

--file [storage_file]
-f [storage_file]        - Path to a file where all changes will be stored
                         - If file exists, it will be used
                         - If file does not exist, it will be created empty

--size [size_MB]
-s [size_MB]             - The virtual.dat file will be size_MB big

--split [split_size_MB]
-p [split_size_MB ]      - Maximum data size per storage_file. Multiple storage files
                           will be created if [size_MB] > [split_size_MB].
                           Beware that actual file size (including index of offsets) may be
                           bigger than split_size_MB, so use max 4088 on FAT32 to be safe.

./dynfilefs -f /tmp/changes.dat -s 1024 -m /mnt
mke2fs -F /mnt/virtual.dat
mount -o loop /mnt/virtual.dat /mnt

./configure
make

DynFileFS can be statically compiled with buildroot, but it's a bit tricky.
Read buildroot/README for more information. Tested on buildroot-2022.02.8
Pre-built static binary for newest version can be found in ./static/ directory.