Hello Guix, I would like to replace the Mesa package in my Xorg configuration. I tried to do this with the following snippet: ``` (modify-services %desktop-services (slim-service-type config => (slim-configuration (inherit config) (xorg-configuration (xorg-configuration (server (replace-mesa xorg-server))))))) ``` But this unfortunately does not work, because the xorg-wrapper uses static paths for the mesa, xkbcomp and xkeyboard-config packages in the derivation. The xserver starts now with the replaced mesa, but some paths still point to the hard coded packages in Guix itself (and not the replacement), which cause some things to not work. This patch changes this to lookup the paths from the inputs of the server field of the xorg-configuration instead. That way the correct paths are setup in the xor-wrapper script. If those inputs are not found for some reason it falls back to the current behavior, using the packages from Guix. Could you please review this? Thanks, Roman.