AWS Lambda /var/task classpath

I am having a problem with no possibility to save files into a /var/task filesystem. If I understand it right, the classpath of lambda is /var/task. I am running a gwt agent in lambda, but it looks for specific file in a classpath. The problem is, that the files that need to be compiled are saved in /var/tmp. So to gwt agent gives an error. "Unable to find file.xml.gwt on your classpath; could be a typo, or maybe you forgot to include a classpath entry for source?"