webkitgtk: set -DENABLE_JOURNALD_LOG=OFF if !systemdSupport

USE_SYSTEMD was replaced by ENABLE_JOURNALD_LOG:
f1ff3cc0f5

-- Could NOT find Journald (missing: Journald_LIBRARY Journald_INCLUDE_DIR)
CMake Error at Source/cmake/OptionsGTK.cmake:486 (message):
  libsystemd or libelogind are needed for ENABLE_JOURNALD_LOG
Call Stack (most recent call first):
  Source/cmake/WebKitCommon.cmake:220 (include)
  CMakeLists.txt:20 (include)

-- Configuring incomplete, errors occurred!
See also "/build/webkitgtk-2.36.0/build/CMakeFiles/CMakeOutput.log".
See also "/build/webkitgtk-2.36.0/build/CMakeFiles/CMakeError.log".

pkgs/development/libraries/webkitgtk/default.nix

@@ -214,7 +214,7 @@ stdenv.mkDerivation (finalAttrs: {
   ] ++ lib.optionals (lib.versionAtLeast gtk3.version "4.0") [
     "-DUSE_GTK4=ON"
   ] ++ lib.optionals (!systemdSupport) [
-    "-DUSE_SYSTEMD=OFF"
+    "-DENABLE_JOURNALD_LOG=OFF"
   ] ++ lib.optionals (stdenv.isLinux && enableGLES) [
     "-DENABLE_GLES2=ON"
   ];