searching for zlib in configure file

lucas@pablo-desktop:~/qemu-1.6.0$ grep "zlib" configure -C 3
libusb=""
usb_redir=""
glx=""
zlib="yes"
guest_agent=""
want_tools="yes"
libiscsi=""
--
  ;;
  --enable-usb-redir) usb_redir="yes"
  ;;
  --disable-zlib-test) zlib="no"
  ;;
  --enable-guest-agent) guest_agent="yes"
  ;;
--
fi

##########################################
# zlib check

if test "$zlib" != "no" ; then
    cat > $TMPC << EOF
#include <zlib.h>
int main(void) { zlibVersion(); return 0; }
EOF
    if compile_prog "" "-lz" ; then
        :
    else
        error_exit "zlib check failed" \
            "Make sure to have the zlib libs and headers installed."
    fi
fi
libs_softmmu="$libs_softmmu -lz"
lucas@pablo-desktop:~/qemu-1.6.0$ CFLAGS=/home/lucas/zlib-1.2.8/zlib-build/include:CFLAGS
lucas@pablo-desktop:~/qemu-1.6.0$ LDFLAGS=/home/lucas/zlib-1.2.8/zlib-build/lib:LDFLAGS