Add Dockerfile for CI system and hook into GitHub Actions

[btashton]

This is a reworking of the Docker container to be used with the GitHub Action CI job for github.com/apache/incubator-nuttx

This should likely replace the PR #13 producing a more modular and smaller docker image. This will also build the docker image on a PR, but will also publish it to this project only on merge.

[btashton]

@liuguo09 Sorry it took me so long to get this together after I pointed you at my proof of concept. I was trying to get some extra build caching things done with it via Github Actions but it seems there docker registry does not support it. I still have some basic cache enabled that will only be used if the registry starts supporting it in the future, otherwise it just warns and moves on with the build.

[xiaoxiang781216]

How about we install esp32 tools here too?

[xiaoxiang781216]

apache/nuttx#437

[liuguo09]

@liuguo09 Sorry it took me so long to get this together after I pointed you at my proof of concept. I was trying to get some extra build caching things done with it via Github Actions but it seems there docker registry does not support it. I still have some basic cache enabled that will only be used if the registry starts supporting it in the future, otherwise it just warns and moves on with the build.

@btashton Thanks for your great work. As to the caching things, we could refine them later once supported by github docker registry. When this PR merged and the new docker image available, we could replace my own liuguo09/ubuntu-nuttx docker to make the CI more official and efficient : )