Make sure Git is installed and path has been setup. If correctly setup the following command will work.
git version
with the returning value being something like
git version x.x.x.y.x
Open a CLI (Terminal, CMD, etc.) to this project and then run the following command
gradlew buildPlugin
This will create the ships plugin for both Bukkit and Sponge. You will find the jar files inside the following folder.
build/