add build for ARM platform

[wholtz]

No description provided.

[wholtz]

I am interested in having a ARM version of this image. I am aware this has been asked for before, but two things have changed since an ARM version was last requested:

1. The previously suggested ARM image is no longer being maintained
2. Use of containers on ARM based systems has increased due to Apple moving to ARM and cloud providers pushing inexpensive ARM instances.

I have verified that:

1. The current Dockerfile does build on my Apple M2 laptop and via Github Actions (on my fork)
2. The little bit of glibc-dependent software that I tested within the ARM image worked

[frol]

@wholtz I am surprised that you claim that it works for you as the package https://github.com/sgerrand/alpine-pkg-glibc/releases/ is only built for amd64. In fact, given that the package is not actively maintained anymore, I would suggest including package building as a stage of the Dockerfile we have here. Would you be willing to work on it?