Suppress stdout from ./configure
Suppress stdout from ./configure

This is recommended by the [Bazel
docs](https://docs.bazel.build/versions/master/be/general.html#general-advice):

> Do not write informational messages to stdout or stderr. While useful
> for debugging, this can easily become noise; a successful genrule
> should be silent. On the other hand, a failing genrule should emit
> good error messages.

nelhage/rules_boost,nelhage/rules_boost