Move s6-overlay around and use ADD

Dockerfile

@@ -8,18 +8,6 @@ ENV ARCH=amd64 \
   POSTGRES_USER=guacamole \
   POSTGRES_DB=guacamole_db
 
-# Apply the s6-overlay
-
-RUN curl -SLO "https://github.com/just-containers/s6-overlay/releases/download/v1.20.0.0/s6-overlay-${ARCH}.tar.gz" \
-  && tar -xzf s6-overlay-${ARCH}.tar.gz -C / \
-  && tar -xzf s6-overlay-${ARCH}.tar.gz -C /usr ./bin \
-  && rm -rf s6-overlay-${ARCH}.tar.gz \
-  && mkdir -p ${GUACAMOLE_HOME} \
-    ${GUACAMOLE_HOME}/lib \
-    ${GUACAMOLE_HOME}/extensions
-
-WORKDIR ${GUACAMOLE_HOME}
-
 # Install dependencies
 RUN apt-get update && apt-get install -y \
     libcairo2-dev libjpeg62-turbo-dev libpng-dev \
@@ -30,10 +18,25 @@ RUN apt-get update && apt-get install -y \
     ghostscript build-essential postgresql-${PG_MAJOR} \
   && rm -rf /var/lib/apt/lists/*
 
+
+# Apply the s6-overlay
+ADD https://github.com/just-containers/s6-overlay/releases/download/v2.2.0.3/s6-overlay-${ARCH}.tar.gz /tmp
+RUN tar -xzf /tmp/s6-overlay-${ARCH}.tar.gz -C /
+RUN tar -xzf /tmp/s6-overlay-${ARCH}.tar.gz -C /usr ./bin
+RUN rm -rf /tmp/s6-overlay-${ARCH}.tar.gz
+
+RUN mkdir -p ${GUACAMOLE_HOME} \
+    ${GUACAMOLE_HOME}/lib \
+    ${GUACAMOLE_HOME}/extensions
+
+WORKDIR ${GUACAMOLE_HOME}
+
 # Link FreeRDP to where guac expects it to be
 RUN [ "$ARCH" = "armhf" ] && ln -s /usr/local/lib/freerdp /usr/lib/arm-linux-gnueabihf/freerdp || exit 0
 RUN [ "$ARCH" = "amd64" ] && ln -s /usr/local/lib/freerdp /usr/lib/x86_64-linux-gnu/freerdp || exit 0
+
 RUN echo $PATH
+
 # Install guacamole-server
 RUN curl -SLO "http://apache.org/dyn/closer.cgi?action=download&filename=guacamole/${GUAC_VER}/source/guacamole-server-${GUAC_VER}.tar.gz" \
   && tar -xzf guacamole-server-${GUAC_VER}.tar.gz \