cleanup: tell Bazel to ignore build directories (#48)
cleanup: tell Bazel to ignore build directories (#48)

For folks that like to type `bazel build ...` we need to instruct Bazel
to ignore the build directories. These may contain test BUILD files that
are only usable in a Docker image or otherwise not usable from the
top-level directory.
googleapis/google-cloud-cpp-common,googleapis/google-cloud-cpp-common,googleapis/google-cloud-cpp-common,googleapis/google-cloud-cpp-common