Provide 'official' docker images for yosys, nextpnr and icestorm

[eine]

Refs: #466, #829, #1152 and #1285.

Although there are multiple docker images available (https://hub.docker.com/search?q=yosys&type=image), AFAIK there is no 'official' one which is built in some CI service managed by the maintainers of this repo/org.

@cliffordwolf mentioned https://hub.docker.com/r/openfpga/icetools in #466, but it seems that the WIP did not take off.

In #1285, a job is added to Travis, where an image containing yosys is built. It would be straightforward to add two more dockerfiles/images for nextpnr and icestorm.

However, the namespace in a docker registry needs to be managed, and some credentials are needed in order to push docker images from travis to dockerhub. Note that a 'machine' or 'bot' account can be used.

For example, projects ghdl and VUnit, both have separate repos for this purpose: ghdl/docker, VUnit/docker. Precisely, this request is related to ghdl/ghdl-yosys-plugin#31.

Furthermore, it'd be possible to provide multiarch images (e.g. amd64, arm32v7 and arm64v8), so ready-to-use containers are available for any user running GNU/Linux, Windows macOs, SBCs, etc. See dbhi/qus.

Note that, for now, iceprog wouldmight still be required on the host. On GNU/Linux, it is probably possible to let a container configure an FPGA through USB/FTDI; but I don't expect it to work on for Windows or macOS, see https://github.com/ghdl/docker/tree/master/usbip.

/cc @q3k

[emilazy]

Since these are all packaged in nixpkgs, I think that Nixery should already provide this as something like nixery.dev/shell/yosys/symbiyosys/nextpnr/icestorm/trellis.

(edit: ah, unfortunately Nixery tracks the stable NixOS branch by default and the versions in nixos-unstable are far more recent, so this isn't a good solution at present.)

[eine]

@emilazy, thanks for the reference! I didn't know about Nixery. I tried nixery.dev/shell/yosys/icestorm on Docker Desktop (Windows 10) and it works! It seems to be quite slow the first time you request to pull an image. Is it because the image is built/compiled on-demand (including all the packages)?

As you said, it is not the solution I want, because I'd like to use latest/development version. Nonetheless, I think that any section about Docker in the docs should mention it.

BTW, do you know why ghdl is not available in nixpkgs? There are some 'old' commits (https://github.com/NixOS/nixpkgs/search?q=ghdl&type=Commits), but nixery.dev/shell/ghdl does not work.

[eine]

Closing in favour of hub.docker.com/u/yosyshq and hdl/containers.