Add a CI test that exercises bazel builds
Add a CI test that exercises bazel builds

If it's not tested, then it doesn't work.  Add a CI test that
executes `bazel build //...` and `bazel test //...`, in addition to
the non-bazel build system.

google/go-jsonnet,google/go-jsonnet,google/go-jsonnet,google/go-jsonnet,google/go-jsonnet