This fixes gnss out of the box on the librem 5, by configuring geoclue
to use gnss-share as a nmea source.
I went this route, of overriding a .service file that invokes geoclue
with a command line option, because forking this .service file is much
nicer than forking geoclue.conf. The conf file will likely change over
time to add new app permissions or whatever, and it's unlikely
(hopefull!) that this .service file will change much upstream...
[ci:skip-build] already built successfully in CI
