I found the solution for this problem. Use maven-dependency-plugin to unpack the project2 jar and then use maven-resources-plugin to extract the project2.changelog-1.0.xml into project1->src->main->resources.
After extracting use tag to include project2.changelog-1.0.xml. in project1.changelog-1.0.xml.
This solved my problem. I'm not sure if this is expensive but i think it's a good solution.