Fix detecting dragonfly triple
Fix detecting dragonfly triple

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