fchdir

pub fn fchdir(fd: posix.fd_t) FchdirError!void {
    if (fd == posix.AT.FDCWD) return;
    const syscall: Syscall = try .start();
    while (true) switch (posix.errno(posix.system.fchdir(fd))) {
        .SUCCESS => return syscall.finish(),
        .INTR => {
            try syscall.checkCancel();
            continue;
        },
        .ACCES => return syscall.fail(error.AccessDenied),
        .NOTDIR => return syscall.fail(error.NotDir),
        .IO => return syscall.fail(error.FileSystem),
        .BADF => |err| return syscall.errnoBug(err),
        else => |err| return syscall.unexpectedErrno(err),
    };
}