Proper FFI compilation.

Dockerfile

@@ -8,8 +8,12 @@ ENV REDMINE_SEND_REMINDERS_DAYS=0 \
 	REDMINE_SEND_REMINDERS_CRON_EXPR="0 7 * * 1-5"
 
 RUN apt-get update \
-	&& apt-get install -y cron ruby-ffi \
+	&& apt-get install -y cron gcc make \
+	# Compile FFI module \
+	&& chmod 770 /usr/local/bundle/gems /usr/local/bundle/extensions/x86_64-linux /usr/local/bundle/extensions/x86_64-linux/3.1.0	\
+	&& bundle check || bundle install \
 	# Clean-up \
+	&& apt-get purge -y --auto-remove gcc make \
 	&& apt-get clean \
 	&& rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/* ~/.cache \
 	# Remove default cron mess \