Trying a new thread/subject as the problem was introduced by the cmake change...
Initially there were two directories but playing around with doxygen STRIP_FROM_PATH settings got it down to one:
49373300 build (rawhide, zipios-2.2.5.0-1.fc34.src.rpm): open (
buildvm-ppc64le-21.iad2.fedoraproject.org) -> FAILED: BuildError: The following noarch package built differently on different architectures: zipios-doc-2.2.5.0-1.fc34.noarch.rpm
rpmdiff output was:
removed /usr/share/doc/zipios/html/dir_32504400af4b8c553a85c61a7ef01dea.html
added /usr/share/doc/zipios/html/dir_dd208edd458824e9eaf902c6da16200d.html