llynx: widevine firefox fix

hosts/llynx/configuration.nix

@@ -25,6 +25,10 @@
   # Install/enable all proprietary firmware
   hardware.enableAllFirmware = true;
 
+  environment.sessionVariables.MOZ_GMP_PATH = [
+    "${pkgs.widevine-cdm}/share/google/chrome/WidevineCdm/manifest.json"
+  ];
+
   snowhawk = {
     filesystem.enable = true;
     user.enable = true;