utils: fix the installation of ffsb binary

Commit a8846217ff4aa2b6063725504bccaad5602fe43a made
ffsb binary non-installable.

Therefore ext4-* test cases fail with:
ext4-uninit-groups    1  TFAIL  :  Test broken: ffsb: command not found

Fixed this by introducing a new Makefile target for ffsb in utils directory.

Signed-off-by: Stanislav Kholmanskikh <stanislav.kholmanskikh@oracle.com>