MINOR: init: setenv HAPROXY_CFGFILES

Set the HAPROXY_CFGFILES environment variable which contains the list of
configuration files used to start haproxy, separated by semicolon.
diff --git a/src/haproxy.c b/src/haproxy.c
index a47b7dd..dcb515d 100644
--- a/src/haproxy.c
+++ b/src/haproxy.c
@@ -1571,6 +1571,7 @@
 
 	/* in wait mode, we don't try to read the configuration files */
 	if (!(global.mode & MODE_MWORKER_WAIT)) {
+		struct buffer *trash = get_trash_chunk();
 
 		/* handle cfgfiles that are actually directories */
 		cfgfiles_expand_directories();
@@ -1582,6 +1583,11 @@
 		list_for_each_entry(wl, &cfg_cfgfiles, list) {
 			int ret;
 
+			if (trash->data)
+				chunk_appendf(trash, ";");
+
+			chunk_appendf(trash, "%s", wl->s);
+
 			ret = readcfgfile(wl->s);
 			if (ret == -1) {
 				ha_alert("Could not open configuration file %s : %s\n",
@@ -1603,6 +1609,9 @@
 			ha_alert("Fatal errors found in configuration.\n");
 			exit(1);
 		}
+		if (trash->data)
+			setenv("HAPROXY_CFGFILES", trash->area, 1);
+
 	}
 	if (global.mode & MODE_MWORKER) {
 		int proc;