depends flex &&

optional_depends udev \
                 "--with-udev" \
                 "--without-udev" \
                 "for udev integration" &&

optional_depends xen \
                 "--with-xen" \
                 "--without-xen" \
                 "for Xen integration" &&

optional_depends bash-completion \
                 "--with-bashcompletion" \
                 "--without-bashcompletion" \
                 "for programmable bash completion"