Cleanup Dockerfile. NFC. (#569)

- Remove unnecessary dependencies from build stage.
- Move binutils installation to first layer.
- Adjust indents and spacing.
- Merge ENV declarations into a single line.
- Split apt-get commands over multiple lines

docker/Dockerfile

@@ -6,17 +6,16 @@ ENV EMSDK /emsdk
 # ------------------------------------------------------------------------------
 
 RUN echo "## Start building" \
-    \
     && echo "## Update and install packages" \
     && apt-get -qq -y update \
     && apt-get -qq install -y --no-install-recommends \
-            libxml2 \
-            wget \
-            git-core \
-            ca-certificates \
+        binutils \
         build-essential \
+        ca-certificates \
         file \
-            python3 python3-pip \
+        git \
+        python3 \
+        python3-pip \
     && echo "## Done"
 
 RUN echo "## Get EMSDK" \
@@ -36,10 +35,8 @@ RUN cd ${EMSDK} \
     && cat ${EMSDK}/upstream/emscripten/cache/sanity.txt \
     && echo "## Done"
 
-# Clean up emscripten installation and strip some symbols
-RUN echo "## Aggresive optimization: Remove debug symbols" \
-&&  apt-get -qq -y update && apt-get -qq install -y --no-install-recommends \
-        binutils \
+# Cleanup Emscripten installation and strip some symbols
+RUN echo "## Aggressive optimization: Remove debug symbols" \
     && cd ${EMSDK} && . ./emsdk_env.sh \
     # Remove debugging symbols from embedded node (extra 7MB)
     && strip -s `which node` \
@@ -62,10 +59,10 @@ COPY --from=stage_build /emsdk /emsdk
 # Fallback in case Emscripten isn't activated.
 # This will let use tools offered by this image inside other Docker images
 # (sub-stages) or with custom / no entrypoint
-ENV EMSDK_NODE=/emsdk/node/12.18.1_64bit/bin/node
-ENV EMSDK=/emsdk
-ENV EM_CONFIG=/emsdk/.emscripten
-ENV PATH="${EMSDK}:${EMSDK}/upstream/emscripten:${EMSDK}/upstream/bin:emsdk/node/12.18.1_64bit/bin:${PATH}"
+ENV EMSDK=/emsdk \
+    EM_CONFIG=/emsdk/.emscripten \
+    EMSDK_NODE=/emsdk/node/12.18.1_64bit/bin/node \
+    PATH="/emsdk:/emsdk/upstream/emscripten:/emsdk/upstream/bin:/emsdk/node/12.18.1_64bit/bin:${PATH}"
 
 # ------------------------------------------------------------------------------
 # Create a 'standard` 1000:1000 user
@@ -87,8 +84,8 @@ RUN echo "## Create emscripten user (1000:1000)" \
 RUN echo "## Update and install packages" \
     # mitigate problem with create symlink to man for base debian image
     && mkdir -p /usr/share/man/man1/ \
-    \
-    &&  apt-get -qq -y update && apt-get -qq install -y --no-install-recommends \
+    && apt-get -qq -y update \
+    && apt-get -qq install -y --no-install-recommends \
         libxml2 \
         ca-certificates \
         python3 \
@@ -105,7 +102,6 @@ RUN echo "## Update and install packages" \
         libidn11 \
         cmake \
         openjdk-11-jre-headless \
-    \
     # Standard Cleanup on Debian images
     && apt-get -y clean \
     && apt-get -y autoclean \