编译u-boot时出现问题

错误提示是这个
arm-linux-ar/opt/EmbedSky/4.4.6/lib/gcc/arm-embedsky-linux-gnueabi/4.4.6/../../../../arm-embedsky-linux-gnueabi/bin/as: error while loading shared libraries: libz.so.1: cannot open shared object file: No such file or directory
: error while loading shared libraries: libz.so.1: cannot open shared object file: No such file or directory
make[1]: *** [arch/arm/cpu/built-in.o] Error 127
make: *** [arch/arm/cpu] Error 2

什么原因？
是我的交叉编译器没有弄好的原因吗？

执行ubuntu_env_install.sh安装需要的环境包