src: android build fix

ip_mreq_source struct are not defined in Android NDK <= 16, regardless
of the API level.

Fixes: #2633
PR-URL: #2637
Reviewed-By: Saúl Ibarra Corretgé <saghul@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

src/unix/udp.c

@@ -653,7 +653,7 @@ static int uv__udp_set_membership6(uv_udp_t* handle,
 }
 
 
-#if !defined(__OpenBSD__) && !defined(__NetBSD__)
+#if !defined(__OpenBSD__) && !defined(__NetBSD__) && !defined(__ANDROID__)
 static int uv__udp_set_source_membership4(uv_udp_t* handle,
                                           const struct sockaddr_in* multicast_addr,
                                           const char* interface_addr,
@@ -842,7 +842,7 @@ int uv_udp_set_source_membership(uv_udp_t* handle,
                                  const char* interface_addr,
                                  const char* source_addr,
                                  uv_membership membership) {
-#if !defined(__OpenBSD__) && !defined(__NetBSD__)
+#if !defined(__OpenBSD__) && !defined(__NetBSD__) && !defined(__ANDROID__)
   int err;
   struct sockaddr_storage mcast_addr;
   struct sockaddr_in* mcast_addr4;