The base directory and config file name is normally set automatically
when we ask Mono to execute the Main function, but in the case of extensions,
there is no Main function, so these values are not set, causing some
features (reflection-only assembly load) to not work correctly.
https://bugzilla.xamarin.com/show_bug.cgi?id=42784
Usually mono does this for other apps, but not for watchOS (where mono doesn't
use signals at all).
watchOS can still raise signals though, so we need to ignore at least SIGPIPE.