Compiling error - filebuffer v0.4.0: expected `i8`, found `u8`

[yonas]

$ cargo build --release
...
   Compiling filebuffer v0.4.0
error[E0308]: mismatched types
    --> /home/yonas/.cargo/registry/src/github.com-1ecc6299db9ec823/filebuffer-0.4.0/src/unix.rs:64:60
     |
64   |         libc::mincore(buffer as *mut libc::c_void, length, residency_uchar)
     |         -------------                                      ^^^^^^^^^^^^^^^ expected `i8`, found `u8`
     |         |
     |         arguments to this function are incorrect
     |
     = note: expected raw pointer `*mut i8`
                found raw pointer `*mut u8`
note: function defined here
    --> /home/yonas/.cargo/registry/src/github.com-1ecc6299db9ec823/libc-0.2.132/src/unix/bsd/freebsdlike/mod.rs:1539:12
     |
1539 |     pub fn mincore(addr: *const ::c_void, len: ::size_t, vec: *mut ::c_char) -> ::c_int;
     |            ^^^^^^^

For more information about this error, try `rustc --explain E0308`.
error: could not compile `filebuffer` due to previous error
warning: build failed, waiting for other jobs to finish...

OS: FreeBSD 13.1 amd64
Cargo: 1.63.0