cd zlib-1.2.8

CFLAGS="-march=i486 -mtune=i686 -Os -pipe" CXXFLAGS="-march=i486 -mtune=i686 -Os -pipe -fno-exceptions -fno-rtti" ./configure --prefix=/usr

CC="gcc -flto -fuse-linker-plugin -march=i486 -mtune=i686 -Os -pipe" CCX="g++ -flto -fuse-linker-plugin -march=i486 -mtune=i686 -Os -pipe -fno-exceptions -fno-rtti" ./configure --prefix=/usr

Remove "-O3" from Makefile


-rwxr-xr-x    1 root     root         63632 Sep  7 23:47 /usr/lib/libz.so.1.2.7
-rw-r--r--    1 root     root         74862 Jun 10 16:18 /tmp/tcloop/zlib_base-dev/usr/lib/libz.a

standard
-rwxr-xr-x    1 root     root         63828 Sep 22 15:45 /usr/lib/libz.so.1.2.8
-rw-r--r--    1 root     root         75054 Sep 22 15:46 /usr/lib/libz.a

lto
-rwxr-xr-x    1 root     root         63776 Sep 22 15:48 /tmp/pkg/usr/lib/libz.so.1.2.8
-rw-r--r--    1 root     root        416472 Sep 22 15:48 /tmp/pkg/usr/lib/libz.a