Allow the configuration file to be specified via an environment variable.

--- geoclue-2.1.10/src/gclue-config.c	2015-04-07 09:50:07.721074380 +0200
+++ geoclue-2.1.10/src/gclue-config.c	2015-04-07 10:27:26.613171960 +0200
@@ -235,6 +235,11 @@
 gclue_config_init (GClueConfig *config)
 {
         GError *error = NULL;
+	const char *config_file_path;
+
+	config_file_path = g_getenv ("GEOCLUE_CONFIG_FILE");
+	if (config_file_path == NULL)
+	  config_file_path = CONFIG_FILE_PATH;
 
         config->priv =
                 G_TYPE_INSTANCE_GET_PRIVATE (config,
@@ -242,7 +247,7 @@
                                             GClueConfigPrivate);
         config->priv->key_file = g_key_file_new ();
         g_key_file_load_from_file (config->priv->key_file,
-                                   CONFIG_FILE_PATH,
+                                   config_file_path,
                                    0,
                                    &error);
         if (error != NULL) {
ub right'></td></tr></table>
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<tr><td><span title='2019-03-01 16:31:52 +0100'>2019-03-01</span></td><td><a href='/guix/commit/gnu/packages/attr.scm?id=1130929acfff30b3f179e6bb949b1b7d78b85b69'>gnu: attr: Update to 2.4.48.</a><span class='msg-avail'>...</span></td><td>Marius Bakke</td></tr>
<tr><td><span title='2018-03-16 05:02:40 -0400'>2018-03-16</span></td><td><a href='/guix/commit/gnu/packages/attr.scm?id=812cee6a07cb4b4ba4724768f9e745e2b25fe931'>gnu: attr: Use invoke instead of system*.</a><span class='msg-avail'>...</span></td><td>Mark H Weaver</td></tr>
<tr><td><span title='2018-02-16 11:11:40 +0100'>2018-02-16</span></td><td><a href='/guix/commit/gnu/packages/attr.scm?id=340978d7b054dcde6c3334267b40a8293eb0ce85'>gnu: Use HTTPS for supported nongnu.org home pages.</a><span class='msg-avail'>...</span></td><td>Tobias Geerinckx-Rice</td></tr>