Missing /bin/sh (dash) in supermin appliance

Bionic beaver 18.04 libguetfs-tools 1:1.36.13-1ubuntu3:

    sudo apt-get install libguestfs-tools
    mkdir sysroot
    # Just a test file.
    dd if=/dev/urandom of=sysroot/myfile bs=1024 count=1024
    sudo virt-make-fs --format=qcow2 --type=ext2 sysroot sysroot.ext2.qcow2

fails with:

    libguestfs: error: tar_in: write error on directory: /:

Without sudo:

    virt-make-fs --format=qcow2 --type=ext2 sysroot sysroot.ext2.qcow2

fails with:

    libguestfs: error: /usr/bin/supermin exited with error status 1.
    To see full error messages you may need to enable debugging.
    Do:
    export LIBGUESTFS_DEBUG=1 LIBGUESTFS_TRACE=1
    and run the command again. For further information, read:
    http://libguestfs.org/guestfs-faq.1.html#debugging-libguestfs
    You can also run 'libguestfs-test-tool' and post the *complete* output
    into a bug report or message to the libguestfs mailing list.

but I think it is an unrelated problem.

Original command with debug vars:

    sudo LIBGUESTFS_DEBUG=1 LIBGUESTFS_TRACE=1 virt-make-fs --format=qcow2 --size=+200M sysroot/ output.img

attached as a file.