old_contents: def _dummy_cc_toolchain_impl(ctx):
      return [platform_common.ToolchainInfo()]
  
  dummy_cc_toolchain = rule(
      implementation = _dummy_cc_toolchain_impl,
      attrs = {},
  )
  
new_contents: def _dummy_cc_toolchain_impl(ctx):
      # The `all_files` attribute is referenced by rustc_compile_action().
      return [platform_common.ToolchainInfo(all_files = depset([]))]
  
  dummy_cc_toolchain = rule(
      implementation = _dummy_cc_toolchain_impl,
      attrs = {},
  )
  
subject: add all_files to the dummy cc_toolchain (#265)