gegl_0_4: disabling jasper, fixing build

Jasper has been recently marked as insecure and removed from a bunch
of places due to some known vulnerabilities and upstream not moving
forward. This was done in NixOS#73586

This prevents gegl_0_4 from building, as jasper is a runtime dependency
per default. There is an upstream issue for that, but it does not seem
to have made progress yet: https://gitlab.gnome.org/GNOME/gegl/issues/35

(cherry picked from commit c9841ed)

pkgs/development/libraries/gegl/4.0.nix

@@ -105,6 +105,9 @@ stdenv.mkDerivation rec {
     "-Dlibv4l=disabled"
     "-Dlibv4l2=disabled"
     "-Dumfpack=disabled"
+    # Disabled due to multiple vulnerabilities, see
+    # https://github.com/NixOS/nixpkgs/pull/73586
+    "-Djasper=disabled"
   ];
 
   # TODO: Fix missing math symbols in gegl seamless clone.