Always install tmpfiles config.

Bug: https://bugs.gentoo.org/921567
Bug: https://gitlab.nic.cz/knot/knot-resolver/-/issues/886
--- a/meson.build
+++ b/meson.build
@@ -237,9 +237,7 @@ subdir('etc')
 
 
 # Systemd unit files
-if systemd_files != 'disabled'
-  subdir('systemd')
-endif
+subdir('systemd')
 
 
 # Additional files
--- a/systemd/meson.build
+++ b/systemd/meson.build
@@ -12,6 +12,18 @@ systemd_config.set('etc_dir', etc_dir)
 systemd_config.set('run_dir', run_dir)
 systemd_config.set('lib_dir', lib_dir)
 
+## tmpfiles
+tmpfiles = configure_file(
+  input: 'tmpfiles.d/knot-resolver.conf.in',
+  output: 'knot-resolver.tmpfiles',
+  configuration: systemd_config,
+)
+install_data(
+  tmpfiles,
+  rename: ['knot-resolver.conf'],
+  install_dir: systemd_tmpfiles_dir,
+)
+
 if systemd_files == 'enabled'
   ## unit files
   kresd_service = configure_file(
@@ -39,18 +51,6 @@ if systemd_files == 'enabled'
   )
   install_man(kresd_systemd_man)
 
-  ## tmpfiles
-  tmpfiles = configure_file(
-    input: 'tmpfiles.d/knot-resolver.conf.in',
-    output: 'knot-resolver.tmpfiles',
-    configuration: systemd_config,
-  )
-  install_data(
-    tmpfiles,
-    rename: ['knot-resolver.conf'],
-    install_dir: systemd_tmpfiles_dir,
-  )
-
   ## sysusers
   sysusers = configure_file(
     input: 'sysusers.d/knot-resolver.conf.in',
-- 
2.43.0