message: Break up build --define <option_name>=true into two steps:
  1) define bazel config
  build:<bazel_config_name> --define <option_name>s=true
  2) set the config
  build --config=<bazel_config_name>
diff: @@ -383,7 +383,9 @@ def set_build_var(environ_cp,
  var = str(int(get_var(environ_cp, var_name, query_item, enabled_by_default)))
  environ_cp[var_name] = var
  if var == '1':
  - write_to_bazelrc('build --define %s=true' % option_name)
  + write_to_bazelrc(
  + 'build:%s --define %s=true' % (bazel_config_name, option_name))
  + write_to_bazelrc('build --config=%s' % bazel_config_name)
  elif bazel_config_name is not None:
  # TODO(mikecase): Migrate all users of configure.py to use --config Bazel
  # options and not to set build configs through environment variables.
  