While working on reproducible builds for openSUSE, I saw, doxygen picked up
non-determinism from filesystem readdir order and therefore produces variations
in build output

https://rb.zq1.de/compare.factory-20220704/diffs/libzypp-compare.out
https://rb.zq1.de/compare.factory-20220704/diffs/pipewire-compare.out

maybe also
https://rb.zq1.de/compare.factory-20220704/diffs/gnuradio-compare.out
https://rb.zq1.de/compare.factory-20220704/diffs/ldas-tools-framecpp-compare.out
https://rb.zq1.de/compare.factory-20220704/diffs/tesseract-ocr-compare.out
https://rb.zq1.de/compare.factory-20220704/diffs/trilinos-compare.out

At some point, there were also influences from ASLR, but these might have been
solved earlier.

The easiest way to reproduce is to use my 'rbk' tool from
https://github.com/bmwiedemann/reproducibleopensuse/
on a osc checkout

Alternatively, use osc build on two different ext4 filesystems in
OSC_BUILD_ROOT=
or use disorderfs to ensure random readdir order.