libpng交叉编译依赖zlib

libpng交叉编译使用LIBS和CPPFLAGS指定zlib路径

sudo make clean
TOOL=gcc-linaro-4.9.4-2017.01-x86_64_arm-linux-gnueabihf
./configure --host=arm-linux CC=/home/ctools/$TOOL/bin/arm-linux-gnueabihf-gcc --prefix=/opt/mylibs/$TOOL/libpng-1.2.57 LIBS=-L/opt/mylibs/$TOOL/zlib-1.2.11/lib CPPFLAGS=-I/opt/mylibs/$TOOL/zlib-1.2.11/include
sudo make
sudo make install
sudo make clean