diana,
There is no direct connection between Ant and MyEclipse. Ant runs out-of-process, meaning that it’s a stand alone external process to MyEclipse. So the only way to literally add the libraries is to specify their full paths all the way down into the MyEclipse plugins directories…. which would be super ugly.
If you are really set on making your project build with Ant, and not using MyEclipse for it, you might consider downloading the LIBs and putting them in some /lib sub directory *just* for your ant build to use.