anchor.diff:  , python3
   , tzdata
   , fixDarwinDylibNames
  -, introspectionSupport ? stdenv.buildPlatform == stdenv.hostPlatform
  +, withIntrospection ? stdenv.buildPlatform == stdenv.hostPlatform
   , gobject-introspection
   , vala
   }:
  
positive.code:   ] ++ lib.optionals (stdenv.hostPlatform != stdenv.buildPlatform) [
      # provides ical-glib-src-generator that runs during build
      libical
    ] ++ lib.optionals introspectionSupport [
      gobject-introspection
      vala
    ] ++ lib.optionals stdenv.isDarwin [
  
negative.code:     glib
      libxml2
      icu
    ] ++ lib.optionals withIntrospection [
      gobject-introspection
    ];
  
    cmakeFlags = [
      "-DENABLE_GTK_DOC=False"
      "-DGOBJECT_INTROSPECTION=${if withIntrospection then "True" else "False"}"
      "-DICAL_GLIB_VAPI=${if withIntrospection then "True" else "False"}"
    ] ++ lib.optionals (stdenv.hostPlatform != stdenv.buildPlatform) [
      "-DIMPORT_ICAL_GLIB_SRC_GENERATOR=${lib.getDev buildPackages.libical}/lib/cmake/LibIcal/IcalGlibSrcGenerator.cmake"
    ];
  