message: configure: use workspace-relative path to tf_configure_bazelrc
  /.bazelrc is not gitignored anymore so this should help in case the
  import line is accidentally committed. Bazel 0.18.0 will support a new
  'try-import' statement that should be used once 0.18.0 has been out long
  enough.
diff: @@ -257,11 +257,7 @@ def reset_tf_configure_bazelrc(workspace_path):
  if _TF_BAZELRC_FILENAME in l:
  continue
  f.write('%s\n' % l)
  - if is_windows():
  - tf_bazelrc_path = _TF_BAZELRC.replace('\\', '/')
  - else:
  - tf_bazelrc_path = _TF_BAZELRC
  - f.write('import %s\n' % tf_bazelrc_path)
  + f.write('import %%workspace%%/%s\n' % _TF_BAZELRC_FILENAME)
  def cleanup_makefile():
  