New warning on nightly: unexpected_cfgs

Here's an example:

warning: unexpected `cfg` condition name: `ci_arti_stable`
 --> crates/tor-protover/src/lib.rs:4:17
  |
4 | #![cfg_attr(not(ci_arti_stable), allow(renamed_and_removed_lints))]
  |                 ^^^^^^^^^^^^^^
  |
  = help: expected names are: `clippy`, `debug_assertions`, `doc`, `docsrs`, `doctest`, `feature`, `miri`, `overflow_checks`, `panic`, `proc_macro`, `relocation_model`, `sanitize`, `sanitizer_cfi_generalize_pointers`, `sanitizer_cfi_normalize_integers`, `target_abi`, `target_arch`, `target_endian`, `target_env`, `target_family`, `target_feature`, `target_has_atomic`, `target_has_atomic_equal_alignment`, `target_has_atomic_load_store`, `target_os`, `target_pointer_width`, `target_thread_local`, `target_vendor`, `test`, `ub_checks`, `unix`, `windows`
  = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(ci_arti_stable)");` to the top of the `build.rs`
  = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration
  = note: `#[warn(unexpected_cfgs)]` on by default

In general, I'd be in favor of keeping this warning, since it does spot the otherwise easy-to-overlook problem of misspelling a cfg condition. But it does create a warning on every crate we have, because our default lint blob includes these:

#![cfg_attr(not(ci_arti_stable), allow(renamed_and_removed_lints))]
#![cfg_attr(not(ci_arti_nightly), allow(unknown_lints))]

Possible solutions, many of them bad:

As suggested in the warning, use a cargo feature instead.
As suggested in the warning, use a build.rs in every crate to explicitly allow this cfg.
Add a blanket #![allow(unexpected_cfgs)].
Use include! trickery; by default, include a file that has exactly these blobs, but in our CI replace that empty file with something else.
Use a tweaked add_warnings or similar script to adjust the warnings block at CI time.

I think I favor 5.