move lwIP source to sdk and add a build hook instead of variant

tools/sdk/lwip/include/lwip/sntp.h

@@ -0,0 +1,56 @@
+#ifndef LWIP_SNTP_H
+#define LWIP_SNTP_H
+
+#include "lwip/opt.h"
+#include "lwip/ip_addr.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/** The maximum number of SNTP servers that can be set */
+#ifndef SNTP_MAX_SERVERS
+#define SNTP_MAX_SERVERS           3
+#endif
+
+/** Set this to 1 to implement the callback function called by dhcp when
+ * NTP servers are received. */
+#ifndef SNTP_GET_SERVERS_FROM_DHCP
+#define SNTP_GET_SERVERS_FROM_DHCP 0//LWIP_DHCP_GET_NTP_SRV
+#endif
+
+/* Set this to 1 to support DNS names (or IP address strings) to set sntp servers */
+#ifndef SNTP_SERVER_DNS
+#define SNTP_SERVER_DNS            1
+#endif
+
+/** One server address/name can be defined as default if SNTP_SERVER_DNS == 1:
+ * #define SNTP_SERVER_ADDRESS "pool.ntp.org"
+ */
+uint32 sntp_get_current_timestamp();
+char* sntp_get_real_time(long t);
+
+void sntp_init(void);
+void sntp_stop(void);
+
+sint8 sntp_get_timezone(void);
+bool sntp_set_timezone(sint8 timezone);
+void sntp_setserver(u8_t idx, ip_addr_t *addr);
+ip_addr_t sntp_getserver(u8_t idx);
+
+#if SNTP_SERVER_DNS
+void sntp_setservername(u8_t idx, char *server);
+char *sntp_getservername(u8_t idx);
+#endif /* SNTP_SERVER_DNS */
+
+#if SNTP_GET_SERVERS_FROM_DHCP
+void sntp_servermode_dhcp(int set_servers_from_dhcp);
+#else /* SNTP_GET_SERVERS_FROM_DHCP */
+#define sntp_servermode_dhcp(x)
+#endif /* SNTP_GET_SERVERS_FROM_DHCP */
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* LWIP_SNTP_H */