nix 0.30.1 wrongly types Redox's sigaction SaFlags_t as c_ulong, but
relibc and the libc crate both declare sa_flags/SA_* as c_int (nix 0.31
already uses c_int for Redox). With the `kill` feature the nix signal
module is compiled and the u64-vs-i32 mismatch breaks the SaFlags
bitflags (E0308). This was latent (uutils built from cache); the relibc
epoll rebuild forced a clean recompile and surfaced it.
Patch the nix Redox branch before cookbook_cargo, with cargo fetch first
so the registry source exists before patching.
vasilito
ca757f9898