gsettings.m4 copyright

[Po Lu]

m4/gsettings.m4 comes from GLib, which is free software under the
LGPLv2.1, but not under copyright of the FSF.

It doesn't seem to have been modified by Emacs either, and it has no
copyright notice on top, so I couldn't determine whether or not it is
licensed under the LGPLv2.1-or-later, or if it's only under the
LGPLv2.1, as in the COPYING file.

Does anyone know what to do in this case?

Thanks.