Makefile does not properly depend on `.clippy.toml`

[tamird]

Changing the content of .clippy.toml does not provoke make CLIPPY=1 all to re-invoke clippy.

/cc @ojeda

[ojeda]

Yeah, I noticed it too (when I was adding doc-valid-idents for the cleanup series), it is on my TODO list. Thanks!

[ojeda]

Lore: https://lore.kernel.org/rust-for-linux/20250520192034.889415-1-ojeda@kernel.org/

[ojeda]

v2: https://lore.kernel.org/rust-for-linux/20250520195345.905374-1-ojeda@kernel.org/