Selfcompiling static build of sslscan

Uses the fork rbsec/sslscan

Based on Alpine Linux, so the image is quite small.

But to make it even smaller, I switched to a multi-stage build and only copy the static sslscan-binary and an absolute minimal set of files from Alpine Linux into an empty container.

I recommend to use the file sslscan.sh

#!/bin/sh

docker run \
    --rm=true --interactive --tty \
    treibholz/sslscan:latest "$@"

Then it's easy:

./sslscan.sh --help