What you're trying to achieve is not as trivial as you think. Component Linking is a Content Delivery feature and it takes into account a lot of variables, such as "is this component published", "which component template has the highest priority" and if the component is published in multiple pages with the same template priority, "which target page is closest to the current one".
Since you want to resolve this URL at publish time to create a static feed, you cannot use Dynamic Linking for this. A few solutions:
- Make your RSS feed an executable page (rss.aspx or rss.jsp) or execute it via a Filter or Http Module. This would allow you to use dynamic linking
- "Resolve" the Url at publish time by:
- Using "where used" to find pages containing the component
- Determine which pages are actually published so that you don't publish a dead link
- If the component is in multiple published pages, determine which one uses a template with the highest priority
Link resolving is not trivial, as you can see from the above description. A more thorough description is available in the SDL Tridion LiveContent (login required).