meson.build: Install D-Bus policy in /usr/share, not /etc
From https://bugs.debian.org/1006631:
dbus supports policy files in both
/usr/share/dbus-1/system.d
and/etc/dbus-1/systemd
. [The] recently released dbus 1.14.0, officially deprecates installing packages' default policies into/etc/dbus-1/systemd
, instead reserving it for the sysadmin. This is the same idea as the difference between/usr/lib/udev/rules.d
and/etc/udev/rules.d
.