[Bro] Issues with DESTDIR support

[Siwek, Jonathan Luke]

> Sweet!  This looks like it's about 99% there: install completes without
> error.  The main broctl.cfg, broccoli.conf, etc config files are
> installed in /etc/.
> 
> However, it looks like scripts/site/local*.bro files are installed into
> /share/bro/site/

Seems in that change I did yesterday I was mistakenly replacing the install prefix with DESTDIR instead of just prepending to it.  I fixed that in the same branch which you can try out by doing this command in your bro repository (assuming it's the same one from yesterday with the branch already checked out):

    for repo in `find . -type d -name cmake`; do (cd $repo && git pull); done

And then try your build/install and let me know if looks alright to you now?

+Jon