meson: install compat symlinks for systemctl and systemd (#8300)

v2:
- init is a symlink to systemd, not systemctl!

meson.build

@@ -60,7 +60,7 @@ conf.set10('HAVE_SPLIT_USR', split_usr)
 rootprefixdir = get_option('rootprefix')
 # Unusual rootprefixdir values are used by some distros
 # (see https://github.com/systemd/systemd/pull/7461).
-rootprefix_default = get_option('split-usr') ? '/' : '/usr'
+rootprefix_default = split_usr ? '/' : '/usr'
 if rootprefixdir == ''
         rootprefixdir = rootprefix_default
 endif
@@ -87,6 +87,7 @@ datadir = join_paths(prefixdir, get_option('datadir'))
 localstatedir = join_paths('/', get_option('localstatedir'))
 
 rootbindir = join_paths(rootprefixdir, 'bin')
+rootsbindir = join_paths(rootprefixdir, 'sbin')
 rootlibexecdir = join_paths(rootprefixdir, 'lib/systemd')
 
 rootlibdir = get_option('rootlibdir')
@@ -1453,6 +1454,10 @@ executable('systemd',
            install : true,
            install_dir : rootlibexecdir)
 
+meson.add_install_script(meson_make_symlink,
+                         join_paths(rootlibexecdir, 'systemd'),
+                         join_paths(rootsbindir, 'init'))
+
 exe = executable('systemd-analyze',
                  systemd_analyze_sources,
                  include_directories : includes,
@@ -1712,6 +1717,12 @@ exe = executable('systemctl', 'src/systemctl/systemctl.c',
                  install_dir : rootbindir)
 public_programs += [exe]
 
+foreach alias : ['halt', 'poweroff', 'reboot', 'runlevel', 'shutdown', 'telinit']
+        meson.add_install_script(meson_make_symlink,
+                                 join_paths(rootbindir, 'systemctl'),
+                                 join_paths(rootsbindir, alias))
+endforeach
+
 if conf.get('ENABLE_BACKLIGHT') == 1
         executable('systemd-backlight',
                    'src/backlight/backlight.c',