We patch GLib to recognize NIX_GSETTINGS_OVERRIDES_DIR
environment variable as a high priority source of settings
schemas. This is used by NixOS modules for desktop environments
like GNOME to set default values for stuff like background image.
Since dconf-editor uses custom GSettingsSchemaSource,
it bypassed that patch, leading to the dconf-editor
showing different values from what other apps
using the GLib’s default source saw.
Let’s mirror our GLib patch in dconf-editor to fix that.
