package/lxc: fix missing include for va_list

Fixes:
 - http://autobuild.buildroot.org/results/0b90e7dca2984652842832a41abad93ac49a9b86

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
[Thomas: update upstream status]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

(cherry picked from commit 6c9c6e2685b7b376420eda814d249ac393aadbfa)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/lxc/0001-stringutils-include-stdarg-for-va_list.patch

@@ -0,0 +1,30 @@
+From b7df06ad14c04f18b7db5b64d5142b802bf64cb2 Mon Sep 17 00:00:00 2001
+From: Fabrice Fontaine <fontaine.fabrice@gmail.com>
+Date: Mon, 3 Dec 2018 22:18:16 +0100
+Subject: [PATCH] stringutils: include stdarg for va_list
+
+Fixes:
+ - http://autobuild.buildroot.org/results/0b90e7dca2984652842832a41abad93ac49a9b86
+
+Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
+[Upstream status: https://github.com/lxc/lxc/commit/b7df06ad14c04f18b7db5b64d5142b802bf64cb2]
+---
+ src/lxc/string_utils.h | 2 ++
+ 1 file changed, 2 insertions(+)
+
+diff --git a/src/lxc/string_utils.h b/src/lxc/string_utils.h
+index 4065e4e6..d4e633cc 100644
+--- a/src/lxc/string_utils.h
++++ b/src/lxc/string_utils.h
+@@ -20,6 +20,8 @@
+ #ifndef __LXC_STRING_UTILS_H
+ #define __LXC_STRING_UTILS_H
+ 
++#include <stdarg.h>
++
+ #include "config.h"
+ 
+ #include "initutils.h"
+-- 
+2.14.1
+