Fixes access to the build directory mounted into the container when UIDs
don't match.

For Docker, HOME is set in addition to get a more useful value than /
and for consistency with Podman.

Resolves #2362

Using `make container` or, if you don't have automake/gmake on your host
system, `./scripts/container.sh` will build an image for the current
branch your are on and drop you into a shell running inside a container
using that image.

From there all tooling required to work on Gluon is available.

Supports both podman (preferred) and docker.