Dockerfile: sort dependencies, and cleanup apt cache

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

Dockerfile

@@ -9,31 +9,38 @@ RUN dpkg --add-architecture armel \
     && dpkg --add-architecture armhf \
     && dpkg --add-architecture arm64 \
     && dpkg --add-architecture ppc64el \
-    && apt-get update && apt-get install -y \
+    && apt-get update \
+    && apt-get install -y --no-install-recommends \
         build-essential \
+        crossbuild-essential-arm64 \
+        crossbuild-essential-armel \
+        crossbuild-essential-armhf \
+        crossbuild-essential-ppc64el \
         curl \
-    sudo \
         gawk \
         iptables \
         jq \
-    pkg-config \
+        kmod \
         libaio-dev \
         libcap-dev \
-    libprotobuf-dev \
-    libprotobuf-c0-dev \
-    libnl-3-dev \
         libnet-dev \
-    libseccomp2 \
+        libnl-3-dev \
+        libprotobuf-c0-dev \
+        libprotobuf-dev \
         libseccomp-dev \
+        libseccomp-dev:arm64 \
+        libseccomp-dev:armel \
+        libseccomp-dev:armhf \
+        libseccomp-dev:ppc64el \
+        libseccomp2 \
+        pkg-config \
         protobuf-c-compiler \
         protobuf-compiler \
         python-minimal \
+        sudo \
         uidmap \
-    kmod \
-    crossbuild-essential-armel crossbuild-essential-armhf crossbuild-essential-arm64 crossbuild-essential-ppc64el \
-    libseccomp-dev:armel libseccomp-dev:armhf libseccomp-dev:arm64 libseccomp-dev:ppc64el \
-    --no-install-recommends \
-    && apt-get clean
+    && apt-get clean \
+    && rm -rf /var/cache/apt /var/lib/apt/lists/*;
 
 # Add a dummy user for the rootless integration tests. While runC does
 # not require an entry in /etc/passwd to operate, one of the tests uses