unused_deps: support cquery (#1030)
unused_deps: support cquery (#1030)

This commit adds a `-cquery` option to `unused_deps` so that the tool
uses the Bazel `cquery` command to examine the build graph.  This is
useful for workspaces where build configuration is mandatory.

Resolves #1027.
bazelbuild/buildtools,bazelbuild/buildtools,bazelbuild/buildtools,bazelbuild/buildtools,bazelbuild/buildtools