message: Escape captured Windows' `where.exe` output.
  This is in preparation of upgrading to bazel 4.0, which flipped `--incompatible_restrict_string_escapes`.
diff: @@ -24,10 +24,12 @@ def which(repository_ctx, program_name):
  if is_windows(repository_ctx):
  if not program_name.endswith(".exe"):
  program_name = program_name + ".exe"
  - result = execute(repository_ctx, ["C:\\Windows\\System32\\where.exe", program_name])
  - else:
  - result = execute(repository_ctx, ["which", program_name])
  - return result.stdout.rstrip()
  + return execute(
  + repository_ctx,
  + ["C:\\Windows\\System32\\where.exe", program_name],
  + ).stdout.replace("\\", "\\\\").rstrip()
  +
  + return execute(repository_ctx, ["which", program_name]).stdout.rstrip()
  def get_python_bin(repository_ctx):
  """Gets the python bin path.
  