use zlib-ng when available

download-as-tar-gz becomes 2.4x faster in docker

segfaults on windows, so don't use it there

does not affect fedora or gentoo,
since zlib-ng is already system-default on those

also adds a global-option to write list of successful
binds to a textfile, for automation / smoketest purposes

scripts/docker/Dockerfile.ac

@@ -13,7 +13,8 @@ RUN     apk --no-cache add !pyc \
             ffmpeg
 
 COPY    i/dist/copyparty-sfx.py innvikler.sh ./
-RUN     ash innvikler.sh && rm innvikler.sh
+ADD     base ./base
+RUN     ash innvikler.sh ac
 
 WORKDIR /w
 EXPOSE  3923