I'm sorry, but i don't understand what the problem is. Are you getting an error when you run the Ant build, or are you getting an error when you run the application after it was built by Ant? If you are getting an error during the ant build, please post the full build output. If you are getting an error while running the app, please post the command line output or error dialog, or whatever it is that you are seeing.
I believe you're attempting to include a library jar inside an executable jar. Java does not automatically add embedded jars to the classpath, so your driver classes would be un-findable by the runtime classloader.
To make that work, you'd either need to explode the oracle driver jar and copy its contents into the executable jar or create a custom classloader that would look inside the embedded driver jar.
An IDE is no substitute for an Intelligent Developer.