[tracker-miners/abderrahim/systemdunitdir] build: get the systemd user unit dir from pkg-config

[Abderrahim Kitouni <akitouni src gnome org>]

commit acc822bbf0df2b3cd938bc785be88b87445964e7
Author: Abderrahim Kitouni <akitouni gnome org>
Date:   Sat Mar 21 08:42:16 2020 +0100

    build: get the systemd user unit dir from pkg-config
    
    fixes #100

 meson.build | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)
---
diff --git a/meson.build b/meson.build
index dc9ae2aa3..ebf4dd419 100644
--- a/meson.build
+++ b/meson.build
@@ -299,10 +299,11 @@ endif
 
 install_systemd_user_services = false
 if get_option('systemd_user_services') == 'yes' or get_option('systemd_user_services') == 'auto'
-  systemd = dependency('systemd', required: false)
+  systemd = dependency('systemd', version: '>= 242', required: false)
   if systemd.found()
     install_systemd_user_services = true
-    systemd_user_services_dir = join_paths(libdir, 'systemd', 'user')
+    systemd_user_services_dir = systemd.get_pkgconfig_variable('systemduserunitdir',
+                                                               define_variable: ['prefix', 
get_option('prefix')])
   else
     install_systemd_user_services = false
     systemd_user_services_dir = '(not found)'