Errors when building libc 0.2.112 as dep of libstd on FreeBSD

[bjorn3]

This causes the cg_clif CI to fail on FreeBSD: https://cirrus-ci.com/task/6719379466354688?logs=test#L178

error: cannot find attribute `derive` in this scope
  --> /.cargo/registry/src/github.com-1ecc6299db9ec823/libc-0.2.112/src/unix/bsd/freebsdlike/freebsd/mod.rs:49:3
   |
49 | #[derive(PartialEq, Eq)]
   |   ^^^^^^
   |
   = note: consider importing this attribute macro:
           core::prelude::rust_2021::derive
error: cannot find attribute `derive` in this scope
  --> /.cargo/registry/src/github.com-1ecc6299db9ec823/libc-0.2.112/src/unix/bsd/freebsdlike/freebsd/mod.rs:65:3
   |
65 | #[derive(PartialEq, Eq)]
   |   ^^^^^^
   |
   = note: consider importing this attribute macro:
           core::prelude::rust_2021::derive
error: cannot find attribute `derive` in this scope
  --> /.cargo/registry/src/github.com-1ecc6299db9ec823/libc-0.2.112/src/unix/bsd/freebsdlike/freebsd/mod.rs:82:3
   |
82 | #[derive(PartialEq, Eq)]
   |   ^^^^^^
   |
   = note: consider importing this attribute macro:
           core::prelude::rust_2021::derive
error: cannot find attribute `derive` in this scope
  --> /.cargo/registry/src/github.com-1ecc6299db9ec823/libc-0.2.112/src/unix/bsd/freebsdlike/freebsd/mod.rs:98:3
   |
98 | #[derive(PartialEq, Eq)]
   |   ^^^^^^
   |
   = note: consider importing this attribute macro:
           core::prelude::rust_2021::derive
error: cannot find attribute `derive` in this scope
   --> /.cargo/registry/src/github.com-1ecc6299db9ec823/libc-0.2.112/src/unix/bsd/freebsdlike/freebsd/mod.rs:114:3
    |
114 | #[derive(PartialEq, Eq)]
    |   ^^^^^^
    |
    = note: consider importing this attribute macro:
            core::prelude::rust_2021::derive
error: cannot find attribute `derive` in this scope
   --> /.cargo/registry/src/github.com-1ecc6299db9ec823/libc-0.2.112/src/unix/bsd/freebsdlike/freebsd/mod.rs:136:3
    |
136 | #[derive(PartialEq, Eq)]
    |   ^^^^^^
    |
    = note: consider importing this attribute macro:
            core::prelude::rust_2021::derive
error: cannot find attribute `derive` in this scope
   --> /.cargo/registry/src/github.com-1ecc6299db9ec823/libc-0.2.112/src/unix/bsd/freebsdlike/freebsd/mod.rs:169:3
    |
169 | #[derive(PartialEq, Eq)]
    |   ^^^^^^
    |
    = note: consider importing this attribute macro:
            core::prelude::rust_2021::derive
error: cannot find attribute `derive` in this scope
   --> /.cargo/registry/src/github.com-1ecc6299db9ec823/libc-0.2.112/src/unix/bsd/freebsdlike/freebsd/mod.rs:227:3
    |
227 | #[derive(PartialEq, Eq)]
    |   ^^^^^^
    |
    = note: consider importing this attribute macro:
            core::prelude::rust_2021::derive

[JohnTitor]

Should be fixed by #2659. feel free to re-open if my assumption is wrong.