adds support for dragonflybsd buildbot
adds support for dragonflybsd buildbot

rust-lang-deprecated/rust-buildbot,edunham/rust-buildbot,rust-lang/rust-buildbot,edunham/rust-buildbot,edunham/rust-buildbot,rust-lang/rust-buildbot,rust-lang-deprecated/rust-buildbot,rust-lang-deprecated/rust-buildbot,rust-lang/rust-buildbot