An example project how to build Vaadin 7.6 project with plain ANT. The build requires NetBeans and Tomee server (for servlet stuff, JSP etc), but can be easily adjusted to work without NetBeans as well.
As all ANT builds are more or less custom tailored, you are probably more interested about the blog post that covers what was done for this example. You can then adapt all that into your own ANT built project.