Support '--features' in virtual workspace?

[kaiwk]

It seems --features flag work in crate #4860, but doesn't work in the root of virtual workspace.

[flip1995]

See rust-lang/cargo#5364

Clippy does not handle features at all, but just passes every feature flag to cargo and lets cargo handle this. If you get different behavior from cargo check --features abc than cargo clippy --features abc, please report back.