The Makefile no longer passes a build architecture; it set a variable that
does not exist, and the architecture is available at run time.
A plain docker build now stamps neoircd with the tag or short commit:
.dockerignore sends .git, without its config, and the builder takes the
version from the VERSION build arg when given, otherwise from git describe.
With .git present, an empty, dev or unknown version fails the build.
Model: opus-5-5
