units: make systemd-repart.service installable

This essentially adds another layer of configurability:
build disable, this, presence of configuration. The default is
set to enabled, because the service does nothing w/o config.

presets/90-systemd.preset

@@ -19,6 +19,7 @@ enable getty@.service
 enable systemd-timesyncd.service
 enable systemd-networkd.service
 enable systemd-resolved.service
+enable systemd-repart.service
 
 disable console-getty.service
 disable debug-shell.service

units/meson.build

@@ -228,8 +228,7 @@ in_units = [
          'multi-user.target.wants/'],
         ['systemd-vconsole-setup.service',       'ENABLE_VCONSOLE'],
         ['systemd-volatile-root.service',        ''],
-        ['systemd-repart.service',               'ENABLE_REPART',
-         'sysinit.target.wants/ initrd-root-fs.target.wants/'],
+        ['systemd-repart.service',               'ENABLE_REPART'],
         ['user-runtime-dir@.service',            ''],
         ['user@.service',                        ''],
 ]

units/systemd-repart.service.in

@@ -21,5 +21,9 @@ Type=oneshot
 RemainAfterExit=yes
 ExecStart=@rootbindir@/systemd-repart --dry-run=no
 
-# The tool returns 77 if there's no GPT partition table pre-existing
+# The tool returns 77 if there's no existing GPT partition table
 SuccessExitStatus=77
+
+[Install]
+WantedBy=sysinit.target
+WantedBy=initrd-root-fs.target