Binder postBuild ensures `set +x +e`

At some point (clearly the game couldn't have started like this) the Binder VM setup underneath bashcrawl has introduced set -x -e which echos commands (annoying) and quits on any !0 command return-code (unplayable).

I don't actually know how Binder is built so am just assuming this is the place to drop in the antidote.