Hi,

appended is a patch I use on my side to build fvwm reproducible.
It is an adjusted version taken from Xenocara (OpenBSD's X11 tree)
recently commited. Upstream did like the idea but I guess from
their reply that they focus on fvwm3 instead:
  https://github.com/fvwmorg/fvwm/issues/67

Take it or leave it as it is, I don't have the time right now
for QA. Patch attached alone + guix tree applying patch.

*DISCLAIMER*
I have build this package in my trees, so I know the patch itself
works.  Due to some issue with correctly building guix in my old
checkout of it, I can not verify quickly if the guix tree patch I
created builds. Important date upcoming, feel free to fix and add
yourself as Co-Author if it doesn't apply.


Happy hacking.