base: darwintrace: set close-on-exec on darwintrace socket
base: darwintrace: set close-on-exec on darwintrace socket

While there is currently no indication that this has been a significant problem
so far, it could certainly happen. Let's do the safe thing and set
close-on-exec (our socket cannot be used after exec anyway).

git-svn-id: 620571fa9b4bd0cbce9a0cf901e91ef896adbf27@138935 d073be05-634f-4543-b044-5fe20cf6d1d6

macports/macports-base,macports/macports-base,neverpanic/macports-base,danchr/macports-base,neverpanic/macports-base,danchr/macports-base