dockerfile: don't cache fail/fail-targets clones

scripts/docker/fail-base/Dockerfile

@@ -119,10 +119,14 @@ RUN wget http://www.aspectc.org/releases/"$acversion"/ac-bin-linux-x86-64bit-"$a
 ENV PATH=/home/fail/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
 
 # Clone FAIL*
+# Break docker layer cache
+ARG CACHE_DATE=1970-01-01
 # RUN git clone https://github.com/danceos/fail.git
 RUN git clone https://gitea.vps.chriphost.de/christoph/fail
 WORKDIR fail
 
 USER root
+
+# Accept SSH connections
 EXPOSE 22
 CMD ["/usr/sbin/sshd", "-D"]