This Answer record covers how you would build and Test Dropbear.
1) Source the PetaLinux 2016.3 settings script.
2) Create a PetaLinux project.
petalinux-create --template zynqMP -t project -s Xilinx-ZCU102-v2016.3-final.bsp
3) Check whether the Dropbear application is enabled by default or not, it should enable by default.
petalinux-config -c rootfs
Filesystem Packages->console/network ->dropbear
4) Use the petalinux-build command
5) Boot the kernel
6) Once the kernel is up, log in using root as your username and password.
7) ssh to a remote system and again ssh back to the board from the remote machine using root as your username and password.
Log:
$ ssh panus8
Welcome to Ubuntu 14.04.4 LTS (GNU/Linux 3.13.0-32-generic x86_64)
panus8:~% ssh root@10.10.70.1
root@10.10.70.1's password:
root@Xilinx-ZCU102-2016_3:~#