optional_depends zlib \
                 "--with-zlib" \
                 "--without-zlib" \
                 "for zlib support" &&

optional_depends xz-utils \
                 "--with-lzma" \
                 "--without-lzma" \
                 "for LZMA support" &&

optional_depends xen-tools \
                 "--with-xen" \
                 "--without-xen" \
                 "for extended Xen support"
