firefox: Prefix $PATH with xdg_utils

This is required for certain URIs that require launching external
programs (e.g. mailto:, magnet:, or irc:) or setting the default browser
via xdg-settings.

Resolve #92751.

Comparable to #96922.

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

@@ -1,5 +1,5 @@
 { stdenv, lib, makeDesktopItem, makeWrapper, lndir, config
-, replace, fetchurl, zip, unzip, jq
+, replace, fetchurl, zip, unzip, jq, xdg_utils
 
 ## various stuff that can be plugged in
 , flashplayer, hal-flash
@@ -249,6 +249,7 @@ let
             --suffix LD_LIBRARY_PATH ':' "$libs" \
             --suffix-each GTK_PATH ':' "$gtk_modules" \
             --suffix-each LD_PRELOAD ':' "$(cat $(filterExisting $(addSuffix /extra-ld-preload $plugins)))" \
+            --prefix PATH ':' "${xdg_utils}/bin" \
             --prefix-contents PATH ':' "$(filterExisting $(addSuffix /extra-bin-path $plugins))" \
             --suffix PATH ':' "$out${browser.execdir or "/bin"}" \
             --set MOZ_APP_LAUNCHER "${browserName}${nameSuffix}" \