Function setup_child_fds 

pub fn setup_child_fds(
    fds_to_keep: &[BorrowedFd<'_>],
    errpipe_write: BorrowedFd<'_>,
    p2cread: i32,
    p2cwrite: i32,
    c2pread: i32,
    c2pwrite: i32,
    errread: i32,
    errwrite: i32,
    errpipe_read: i32,
) -> Result<()>