The solution is to add your static sitemap to the Liferay document library, and then tell Google the map url using Google Webmaster Tools .
The second solution is to add the sitemap to your ROOT directory (if you are using Tomcat), however this may require some changes to Tomcat settings and Liferay code.
Another solution is to create a portlet that generates all the links you want into a Sitemap XML file, and then save this file in your chosen location. This is the approach I took when I needed to post the full URLs of articles that don't actually exist as pages.
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