Function nix::unistd::mkfifoat  
pub fn mkfifoat<P: ?Sized + NixPath>(dirfd: Option<RawFd>, path: &P, mode: Mode) -> Result<()>The portability is definied by: 
#[cfg(not(any(target_os = "macos", target_os = "ios", target_os = "android",
target_os = "redox")))]