sane: add mkSaneConfig

pkgs/applications/graphics/sane/config.nix

@@ -0,0 +1,27 @@
+{ stdenv }:
+
+{ paths }:
+
+with stdenv.lib;
+let installSanePath = path: ''
+      find "${path}/lib/sane" -not -type d -maxdepth 1 | while read backend; do
+        ln -s $backend $out/lib/sane/$(basename $backend)
+      done
+
+      find "${path}/etc/sane.d" -not -type d -maxdepth 1 | while read conf; do
+        ln -s $conf $out/etc/sane.d/$(basename $conf)
+      done
+
+      find "${path}/etc/sane.d/dll.d" -not -type d -maxdepth 1 | while read conf; do
+        ln -s $conf $out/etc/sane.d/dll.d/$(basename $conf)
+      done
+    '';
+in
+stdenv.mkDerivation {
+  name = "sane-config";
+  phases = "installPhase";
+
+  installPhase = ''
+    mkdir -p $out/etc/sane.d $out/etc/sane.d/dll.d $out/lib/sane
+  '' + concatMapStrings installSanePath paths;
+}

pkgs/top-level/all-packages.nix

@@ -10735,6 +10735,8 @@ let
     hotplugSupport = config.sane.hotplugSupport or true;
   };
 
+  mkSaneConfig = callPackage ../applications/graphics/sane/config.nix { };
+
   saneFrontends = callPackage ../applications/graphics/sane/frontends.nix { };
 
   seafile-shared = callPackage ../misc/seafile-shared { };