Rework sysupdate meson options (#34832)

systemd-sysupdated is still unstable and we'd like to make breaking
changes to it even after the v257 release, so we document it as such and
disable building it by default in release builds. The distro can still
opt-in, and we still build it in developer mode so it has CI coverage

src/sysupdate/meson.build

@@ -40,7 +40,7 @@ executables += [
         libexec_template + {
                 'name' : 'systemd-sysupdated',
                 'dbus' : true,
-                'conditions' : ['ENABLE_SYSUPDATE'],
+                'conditions' : ['ENABLE_SYSUPDATED'],
                 'sources' : files('sysupdated.c'),
                 'dependencies' : threads,
         },
@@ -48,11 +48,11 @@ executables += [
                 'name' : 'updatectl',
                 'public' : true,
                 'sources' : systemd_updatectl_sources,
-                'conditions' : ['ENABLE_SYSUPDATE'],
+                'conditions' : ['ENABLE_SYSUPDATED'],
         },
 ]
 
-if conf.get('ENABLE_SYSUPDATE') == 1
+if conf.get('ENABLE_SYSUPDATED') == 1
         install_data('org.freedesktop.sysupdate1.conf',
                      install_dir : dbuspolicydir)
         install_data('org.freedesktop.sysupdate1.service',