gratitous API change in recent versions of texi2html where
the output directory has changed names.
Fix for:
bug #13026: The build fails with texi2html 1.76
bug #12715: make issues during install
patch #3091: commandline fix for latest version of texi2html
git-svn-id: svn://svn.savannah.nongnu.org/avrdude/trunk@499 81a1dc3b-b13d-400b-aceb-764788c761c2