Instead of returning a custom error, use ErrGetBaseConfigNotSupported
that seems to be intended for this use case. This fixes DNS resolution
on macOS clients compiled from source.
Signed-off-by: Anton Tolchanov <anton@tailscale.com>
This populates DNS suffixes ("ts.net", etc) in /etc/resolver/* files
to point to 100.100.100.100 so MagicDNS works.
It also sets search domains.
Updates #4276
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>