O que é extension location?
Eu achei isso no help:
Installing and uninstalling extensions
The install process for extensions is similar to that for products except for the following differences:
Determine which already-installed product is to be extended (by asking the user or searching the computer for the appropriate marker file)
Create an .eclipseextension marker file (instead of an .eclipseproduct marker file). The format and content are similar to the product markers.
Create a link file for the extension and write it into the links directory of the associated product. The link file has the same name as the extension's feature directory without the version suffix. The link file is a java.io.Properties format file which defines the path to the installed extension.
The uninstall process for extensions is similar to that for products except that the uninstall must remove the link file from any products where it added one.