timedated: add helper macro ZONEINFODIR

Since it's already used twice, and will be used more in the next commits.

src/timedated.c

@@ -51,6 +51,8 @@ static GFile *hwclock_file = NULL;
 static GFile *timezone_file = NULL;
 static GFile *localtime_file = NULL;
 
+#define ZONEINFODIR DATADIR "/zoneinfo"
+
 gboolean local_rtc = FALSE;
 gchar *timezone_name = NULL;
 G_LOCK_DEFINE_STATIC (clock);
@@ -95,7 +97,7 @@ get_timezone_name (GError **error)
 
     /* Log if /etc/localtime is not up to date */
     localtime_filename = g_file_get_path (localtime_file);
-    localtime2_filename = g_strdup_printf (DATADIR "/zoneinfo/%s", ret);
+    localtime2_filename = g_strdup_printf (ZONEINFODIR "/%s", ret);
     localtime2_file = g_file_new_for_path (localtime2_filename);
 
     if (!g_file_load_contents (localtime_file, NULL, &filebuf, NULL, NULL, error)) {
@@ -140,7 +142,7 @@ set_timezone (const gchar *_timezone_name,
     }
 
     localtime_filename = g_file_get_path (localtime_file);
-    localtime2_filename = g_strdup_printf (DATADIR "/zoneinfo/%s", _timezone_name);
+    localtime2_filename = g_strdup_printf (ZONEINFODIR "/%s", _timezone_name);
     localtime2_file = g_file_new_for_path (localtime2_filename);
 
     if (g_file_test(localtime_filename, G_FILE_TEST_IS_SYMLINK)) {