./configure --prefix=/usr/local/gd2/ --with-zlib=/usr/local/zlib/ --with-jpeg=/usr/local/jpeg6/ --with-png=/usr/local/libpng/ --with-freetype=/usr/local/freetype
configure: WARNING: unrecognized options: --with-zlib有个警告，怎么才能解决啊，有安装zlib