Content of cache manifest not correct for multi-project build

Our application is composed of 3 projects within eclipse, a core project that defines low-level classes, a main project that defines custom components (and contains its own widgetset.gwt.xml) and a top-level project that depends on these 2 projects to build the final deployable war file. The widget set in the main project has an entry defined to include some icons in the cache manifest so that they will be available offline.

When the main project is built the cache manifest correctly includes the path to these icons:
CACHE MANIFEST

Build timeTue Sep 02 16:54:47 CEST 2014

CACHE:

…/…/…/…/…/VAADIN/themes/monitor/images/actionbar_status_offline.png

…/…/…/VAADIN/themes/touchkit/styles.css
etc

However, when the top-level project is built the cache manifest does not include the path to these icons.

CACHE:
…/…/…/VAADIN/themes/touchkit/styles.css

I would like to know if there is anything that can be done so that the cache manifest is generated correctly when the top level project is built.