[Bro] error at the time of configure (bro 2.1)

[Siwek, Jonathan Luke]

> I ran into something recently where the little test program that FindPCAP.cmake uses doesn't link with pthread so if someone is using PF_Ring (which requires pthread at link time) the test program will fail.

The test programs in FindPCAP.cmake are meant to determine whether linking libpcap also requires linking a thread library.  It first tests without a thread library, and failing that, then tries with a thread library.  If both ways fail, it gives up.  One reason both ways could fail would be if CMake didn't correctly determine a thread library to link against and libpcap needs it.

But in this case, the ./configure output shows that libpcap links without a thread library and that pcap_get_pfring_id() isn't provided by libpcap, so it's probably not one from PF_Ring.  And the test that is failing is one from PCAPTests.cmake (which links tests the same way that FindPCAP.cmake determines).

>  I hadn't brought it up yet though because it doesn't always seem to fail and I'm not sure what the conditions for failure are yet.

If you can give me a CMake version, PF_Ring version, Bro version, and OS on which it's reproducible, I can look at it.

    Jon