busybox: make httpd work when built with clang

packages/busybox/build-with-clang.patch

@@ -20,3 +20,13 @@ Patch inspired by http://landley.net/mantis/mantis-2344.html
  	less_gets_pos = -1; \
  	empty_line_marker = "~"; \
  	num_files = 1; \
+--- ../httpd.c.orig	2018-06-08 06:06:10.426529411 +0000
++++ ./networking/httpd.c	2018-06-08 06:08:25.886684451 +0000
+@@ -489,6 +489,7 @@
+ #define INIT_G() do { \
+ 	setup_common_bufsiz(); \
+ 	SET_PTR_TO_GLOBALS(xzalloc(sizeof(G))); \
++	asm volatile("":::"memory");
+ 	IF_FEATURE_HTTPD_BASIC_AUTH(g_realm = "Web Server Authentication";) \
+ 	IF_FEATURE_HTTPD_RANGES(range_start = -1;) \
+ 	bind_addr_or_port = "8080"; \