[Build] suppress curl/wget progress bars

In the Jenkins console output, `curl` gives us mountains of `#` symbols as it tries to show its download progress. 

![noise from curl in Jenkins output](http://i.imgur.com/P2E7yUw.png)

I don't think this is useful so I've changed things to suppress these progress bars. If there is actually some use to this, feel free to reject this proposal.