fingerprint error causing rebuild on feature flag changes #3923
Description
Switching between building rocket with and without feature flags causes the cookie dependency to be rebuilt each item. The following logs show this:
$ cargo build
Compiling rocket v0.2.4
Finished dev [unoptimized + debuginfo] target(s) in 21.1 secs
$ cargo build --all-features
Compiling cookie v0.7.4
Compiling rocket v0.2.4
Finished dev [unoptimized + debuginfo] target(s) in 24.31 secs
$ cargo build
Compiling cookie v0.7.4
Compiling rocket v0.2.4
Finished dev [unoptimized + debuginfo] target(s) in 23.16 secs
Running with RUST_LOG=cargo::ops::cargo_rustc::fingerprint=info shows that this is caused by a fingerprint error due to cookie in turn due to ring.
$ RUST_LOG=cargo::ops::cargo_rustc::fingerprint=info cargo build --all-features
INFO:cargo::ops::cargo_rustc::fingerprint: fingerprint error for cookie v0.7.4: new (ring v0.7.5) != old (ring v0.7.5)
Compiling cookie v0.7.4
Compiling rocket v0.2.4
Finished dev [unoptimized + debuginfo] target(s) in 24.29 secs
cc @briansmith