Autoconf: Print the GNU C Library version when needed in autogen.sh

[tcpdump] / tests / dns_tcp-skip-3-c-1.out

    4  2020-06-10 09:21:03.847323 IP 192.168.1.11.33779 > 209.87.249.18.53: Flags [P.], seq 603899917:603899975, ack 2043824404, win 64240, length 58 17177+ [1au] A? www.tcpdump.org. (56)