dynamic zlib library
1. download zlib source code from the following website for new version of it.
2. uncompress it (tar -zxvf zlib-x.x.x.tgz)
3. configure it
./configure -s
4. modify the "Makefile" using the cross toolchain to replace the relative tools (e.g: gcc, ar, ranlib, tar).
5. make.
static library
1. take the same 1,2 steps as up method.
2. won't use "./configure -s"
3. modify the "Makefile"
4. make