[gcr/meson-stuff: 4/6] meson: add falback for systemduserunitdir prefix

[Niels De Graef <nielsdg src gnome org>]

commit 6c6c05d5b3f8b7ffe6137020bb702d8df670b387
Author: Niels De Graef <nielsdegraef gmail com>
Date:   Sun Jun 12 23:36:33 2022 +0200

    meson: add falback for systemduserunitdir prefix

 meson.build | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)
---
diff --git a/meson.build b/meson.build
index a1e08822..e94db021 100644
--- a/meson.build
+++ b/meson.build
@@ -68,7 +68,10 @@ libsystemd_deps = []
 libsystemd = dependency('libsystemd', required: get_option('systemd'))
 systemd = dependency('systemd', required: get_option('systemd'))
 if libsystemd.found() and systemd.found()
-  systemduserunitdir = systemd.get_pkgconfig_variable('systemduserunitdir')
+  systemduserunitdir = systemd.get_variable('systemduserunitdir',
+    pkgconfig_define: [ 'prefix', get_option('prefix') ],
+    default_value: 'lib' / 'systemd' / 'user',
+  )
   libsystemd_deps += libsystemd
   with_systemd = true
 endif