redefinition of 'struct in6_pktinfo' when building on ubi7 with gcc/g++ 9.5.0

[Rhett-Ying]

just run make -j

In file included from send-zerocopy.c:15:                                                                                    
/usr/include/linux/ipv6.h:19:8: error: redefinition of 'struct in6_pktinfo'                                
   19 | struct in6_pktinfo {                                                                                                 
      |        ^~~~~~~~~~~                                                                                                   
In file included from /usr/include/arpa/inet.h:22,                                                                           
                 from send-zerocopy.c:13:                                                                                    
/usr/include/netinet/in.h:538:8: note: originally defined here                                                               
  538 | struct in6_pktinfo                                                                                                   
      |        ^~~~~~~~~~~