refactor docker to support arm32/arm64/amd64 all in one build

docker-install-tini.sh

@@ -0,0 +1,25 @@
+#!/bin/sh
+
+# Figure out latest release via GitHub API
+release=$(curl --silent "https://api.github.com/repos/krallin/tini/releases/latest" | jq -r .tag_name)
+
+# _Reliable_ way to get which arch for tini download
+arch=$(python <<EOF
+from __future__ import print_function
+import platform
+processor = platform.machine()
+if processor == 'aarch64':
+    print('arm64', end='')
+elif processor == 'x86 64' or processor == 'x86_64':
+    print('amd64', end='')
+elif processor == 'armv7l':
+    print('armhf', end='')
+
+EOF
+)
+
+# Download/install tini
+curl -L https://github.com/krallin/tini/releases/download/$release/tini-static-$arch \
+     -o /sbin/tini
+chmod a+x /sbin/tini
+