Merge pull request #206465 from liamdiprose/fix/zrythm-find-fallback-icons

zrythm: add path for fallback icons

pkgs/applications/audio/zrythm/default.nix

···
   preFixup = ''
     gappsWrapperArgs+=(
       --prefix GSETTINGS_SCHEMA_DIR : "$out/share/gsettings-schemas/${pname}-${version}/glib-2.0/schemas/"
+      --prefix XDG_DATA_DIRS : "$XDG_ICON_DIRS"
              )
   '';