Just realized I never posted my final update to this thread, so in case anyone else ever
wanders here looking for answers:
Any precompiled glib schema file is not needed -- if the *.gschema.xml file(s) are moved
to %{buildroot}/%{_datadir}/glib-2.0/schemas/ at the end of the %install section of the
RPM spec. And it would be more standard to move the gschemas there, so you should do it.
So, move the *.gschema.xml files, and then delete gschemas.compiled file. You could even
delete the extension's own schemas subdirectory (under
%{buildroot}/%{_datadir}/gnome-shell/extensions/%{UUID}/ ), because by then it should be
empty.