Skip the discussion until #40921 (comment)

The plan has been updated accordingly

Broad plan

1. Add clippy as a submodule
2. Try to build clippy on every travis run
3. In case of failure, automatically post an issue at the clippy repository linking the offending PR
4. modify src/bootstrap/dist.rs, src/bootstrap/lib.rs and
   src/bootstrap/step.rs to bundle clippy as a rustup component with rustc if clippy builds
5. modify src/tools/build-manifest/src/main.rs
6. open a PR
7. modify rustup to not update if a component is not available (and add a force option to override)

Open Questions

• Configuration works through clippy.toml right now
  • change -Zextra-plugins to take an argument, so we can pass -Zextra-plugins=clippy(clippy.toml)?