To incorporate Doxygen documentation into pipelines.lsst.io, it's become clear that a stack-wide Doxygen build is required, rather than piecing together individual Doxygen builds that are made by scons doc. At the moment, create_xlinkdocs.sh and makeDocs work together to do a stack-wide Doxygen build as part of the run_rebuild Jenkins job. The products of this Doxygen build aren't available to the documenteer Jenkins job.
It seems that the best route forward is to replace the legacy tooling with an integrated build solution in documenteer itself, so that both the Doxygen and Sphinx builds are controlled from one command and one code-base.
The purpose of this ticket is to add this functionality to documenteer, based on the prior art in create_xlinkdocs.sh and makeDocs.
An outcome of this work is that a monolithic Doxygen xml output will be available to Breathe to incorporate C++ API documentation directly into pipelines.lsst.io.
This work will not attempt to build HTML output from Doxygen, nor compile Doxygen pages (.dox) as those are considered legacy output and contents.