gnuchess 6, trouble to build book.bin

Hi,

I'm trying to update the gnuchess Debian package. In Debian, we have two
packages: gnuchess and gnuchess-book, and I'm having trouble building
gnuchess-book with gnuchess 6.

gnuchess-book is built using book_1.02.pgn using this command:

 echo -e "book add book_1.02.pgn\nquit" | gnuchess

With gnuchess 5, it produced a book.dat file which is installed by
gnuchess-book. With gnuchess 6, gnuchess does not wait for the book add
command to finish before exiting, so the book is not built. And I could
not find another easy way to build the book.

Do you have any idea ? Or could you please fix gnuchess so that we could
build the book as in gnuchess 5.

Thanks,
Vincent