firefox: add pname to throw message

https://github.com/NixOS/nixpkgs/pull/164646#discussion_r835879348

pkgs/applications/networking/browsers/firefox/common.nix

@@ -127,7 +127,7 @@
 }:
 
 assert stdenv.cc.libc or null != null;
-assert pipewireSupport -> !waylandSupport || !webrtcSupport -> throw "pipewireSupport requires both wayland and webrtc support.";
+assert pipewireSupport -> !waylandSupport || !webrtcSupport -> throw "${pname}: pipewireSupport requires both wayland and webrtc support.";
 
 let
   flag = tf: x: [(if tf then "--enable-${x}" else "--disable-${x}")];