add_custom_target() output
Using the Jenkins Warnings Next Generation plugin my jobs fail because the output from Doxygen is broken. But I have found that this only happens when running Doxygen via cmake's doxygen_add_docs(), not directly.
What seems to happen is that add_custom_target() redirects the COMMAND stderr to stdout in such a way that the stderr output can appear in the middle of a line of stdout output, making it unreadable to a person... and unparsable by the Warnings Next Generation plugin.
cmake 3.19.2