I am trying to setup PPPoS connection using lwip on Xilinx SDK 2018.1, But i am getting an error - undefined reference to pppos_create function

Question

I have already configured zcu-102 and linux system using uart16550 scuccefully. Now i wanted to connect them through PPPoS (Point to point Protocol over serial connection) from lwip202 library. But when i try to build my code, i get

undefined reference to 'pppos_create' 
undefined reference to 'ppp_connect' 

Things i have already tried:

1. Enabled Lwip202 in BSP settings.

2. Enabled PPP_SUPPORT by changing its value from '0' to '1' in netif/ppp/ppp_opts.h

3. Also have included the "ppp.h", "pppos.h", "lwipopts.h" in my main.c file.

4. Also defined PPP_SUPPORT as 1 in "lwipopts.h" as it was not there by default.

PS: cntrl + left click on the pppos_create function does take me to the source file i.e., pppos.h which means that the pppos.h file is indeed linked to the project.

Please help.. Thanks.