How to set custom location for urdf files created from xacro with cmake?

edit

The mentioned tutorial, as well as with the software, xacro, has been updated a lot since the OP's post. AFAICS the things asked are covered in the tutorial now.

automatically build urdf files from CMakeLists.txt, but I would additionally wish to create the files into a custom location, and could not make it work by myself... I tried setting the RUNTIME_OUTPUT_DIRECTORY but it did not have any effect.

Not sure what you exactly want to achieve but I assume you want URDF files to be installed in a designated path. The tutorial reads:

New in Jade: While this cmake code provides full control over the target name and build order, there is a conveniency macro too:

xacro_add_files(${xacro_files} TARGET media_files)

Next,

I don't think it is the way forward as I want the urdf files in a separate location and everything else built from the CMakeLists.txt in their respective directories. Is there a way to modify the aforementioned tutorial to create a custom directory for the urdf files?

Not sure what you mean...But I guess the cmake macro above allows you to install the URDF files into the "custom directory".