An application using LwIP would not build in 3.1.2 on Linux because of wrong wiced_network.c file.
From the error there is a reference to the NX_IP data structure not belonging to LwIP:
> WICED/network/LwIP/WICED/wiced_network.c:81:1: error: unknown type name 'NX_IP'
> NX_IP* wiced_ip_handle[ 3 ] =
After copying over the WICED/network/LwIP/WICED/wiced_network.c file from MacOS distribution it built with no errors.