Add unistd safe rules

[lucic71]

No description provided.

[nunoplopes]

is this dependency needed here?

[nunoplopes]

drop the .1

[lucic71]

Done

[nunoplopes]

I meant this one is not needed

[lucic71]

Both libcc2rs and libc-dep depend on libc. Adding nix to libc-dep pulls libc with extra traits. This creates a mismatch between the libc version that libcc2rs uses and the one that libc-dep uses.

To unify the libc versions from libcc2rs and libc-dep, I added nix as a dependency in libcc2rs as well.

Without this, weird errors like the following one appear:

error[E0308]: mismatched types                                                                 
   --> main.rs:40:30                       
    |                                                                                          
 40 |     assert!(((((libc::fileno(libcc2rs::stderr_unsafe())) == (2)) as i32) != 0));
    |                 ------------ ^^^^^^^^^^^^^^^^^^^^^^^^^ expected `FILE`, found `libc::unix::FILE`
    |                 |
    |                 arguments to this function are incorrect
    |
note: there are multiple different versions of crate `libc` in the dependency graph
   --> /root/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/libc-0.2.186/src/macros.rs:259:9
    |
259 |           pub enum $i { }
    |           --------------- this is the found type
    |
   ::: /root/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/libc-0.2.186/src/macros.rs:259:9
    |
259 |           pub enum $i { }
    |           ^^^^^^^^^^^^^^^ this is the expected type
    |
   ::: /root/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/libc-0.2.186/src/unix/mod.rs:596:1
    |
596 | / extern_ty! {
597 | |     pub enum FILE {}
598 | | }
    | |_- in this macro invocation
    = help: you can use `cargo tree` to explore your dependency tree