On VPN, puller fails to resolve dns name on MacOS

When puller is used to pull a docker image over VPN on MacOS. The root cause seem to be [this issue](https://github.com/golang/go/issues/12524). Apparently the go_library definition need to have `cgo=True` for this to work on Mac.

So, to summarize the issue, the host name resolution is not honoring Mac's DNS configuration, instead it is always reading `/etc/resolv.conf` to get the name servers.