build: make embedded pi images reproducible

docker/smoke/core-smoke.sh

@@ -1,7 +1,8 @@
 #!/bin/sh
 set -eu
 
-test "$(id -u)" != "0"
+test "$(id -u)" = "10001"
+test -n "${PI_VERSION:-}"
 
 node_version="$(node --version)"
 python_version="$(python --version 2>&1)"
@@ -15,7 +16,10 @@ case "$python_version" in
 esac
 
 tht --help >/dev/null
-pi --version >/dev/null
+test "$(pi --version)" = "$PI_VERSION"
+test ! -e /var/run/docker.sock
+touch /data/.core-smoke-writable
+rm /data/.core-smoke-writable
 
 /app/docker/core-entrypoint.sh server &
 server_pid=$!