See mantisbt-dev.git script docbook-manual.py and docbook-manual-repo.py for scripts to automate this task.

http://git.mantisbt.org/?p=mantisbt-dev.git;a=tree

Automated documentation builds of latest developer documentation are available at http://www.mantisforge.org/dev/manual/

Documentation for live releases is automatically build and published on http://www.mantisbt.org

Reopening since it is about the new Hudson/Phing based build-system.

Setting to resolved / won't fix as there is no plan to migrate to a Phing based build system.
Let's go on using Travis CI and our local builds scripts until someone starts working on another solution.