Hi Christophe.
Very sorry for the delayed reply.
I tried to make an itemized list by writing the following in a Texinfo file:
@itemize @w{}
@item @option{--build=} platform on which the program is compiled,
...
This works for me with the current texinfo.tex.
Maybe you had an older version?
Try the one at http://ftp.gnu.org/gnu/texinfo/texinfo.tex.
If you have the current texinfo.tex and yet it's still failing, please
send me a complete example input file, since something else must be
going on.
Thanks,
Karl