systemd/knot-resolver.service.in: generalize paths

I can't see why not.  Also avoid unnecessary /usr/bin/env
kresd doesn't work well without `ninja install` anyway.

bindir: maybe we should install the python binaries into sbin instead.
We're also being slightly inconsistent - allowing to override some
directories by meson but not respecting it for the python stuff.

meson.build

@@ -53,6 +53,7 @@ etc_dir = prefix / get_option('sysconfdir') / 'knot-resolver'
 lib_dir = prefix / get_option('libdir') / 'knot-resolver'
 modules_dir = lib_dir / 'kres_modules'
 sbin_dir = prefix / get_option('sbindir')
+bin_dir = prefix / get_option('bindir')
 run_dir = '/run' / 'knot-resolver'
 systemd_work_dir = prefix / get_option('localstatedir') / 'lib' / 'knot-resolver'
 systemd_cache_dir = prefix / get_option('localstatedir') / 'cache' / 'knot-resolver'

systemd/knot-resolver.service.in

@@ -9,14 +9,14 @@ Wants=nss-lookup.target
 [Service]
 Type=notify
 TimeoutStartSec=10s
-ExecStart=/usr/bin/env knot-resolver --config=/etc/knot-resolver/config.yml
+ExecStart=@bin_dir@/knot-resolver --config=@etc_dir@/config.yml
+ExecReload=@bin_dir@/kresctl --socket @run_dir@/manager.sock reload
 KillSignal=SIGINT
-WorkingDirectory=/var/run/knot-resolver/
+WorkingDirectory=@systemd_work_dir@
 User=@user@
 Group=@group@
 CapabilityBoundingSet=CAP_NET_BIND_SERVICE CAP_SETPCAP
 AmbientCapabilities=CAP_NET_BIND_SERVICE CAP_SETPCAP
-ExecReload=/usr/bin/env kresctl --socket /var/run/knot-resolver/manager.sock reload
 
 [Install]
 WantedBy=multi-user.target
\ No newline at end of file

systemd/meson.build

@@ -8,6 +8,7 @@ systemd_config.set('group', group)
 systemd_config.set('systemd_work_dir', systemd_work_dir)
 systemd_config.set('systemd_cache_dir', systemd_cache_dir)
 systemd_config.set('sbin_dir', sbin_dir)
+systemd_config.set('bin_dir', bin_dir)
 systemd_config.set('etc_dir', etc_dir)
 systemd_config.set('run_dir', run_dir)
 systemd_config.set('lib_dir', lib_dir)