scratch docker amd64

[protolambda]

This is a draft to make the docker image smaller and more minimal by:

• using an alpine linux for the build stage
• producing a static binary
• using scratch for the running image stage

The result should be about a 20MB docker image:

Previously this was 100MB:

My concern now is testing the new image, and making sure it still works on ARM, Windows, Mac. Any users that like to beta test?

Beta image, if you don't want to build it yourself, here: protolambda/eth2stats-client:scratch (docker hub)

[tzapu]

i tested this on a rpi4/ubuntu 64bits and unfortunately it looks like it's not working

Digest: sha256:05206b88a51bbb40abba04a9d5a9d0fe4a6dd8f7a622aea1f1f713701be26174
Status: Downloaded newer image for protolambda/eth2stats-client:scratch
Creating medalla-eth2stats ... done
Attaching to medalla-eth2stats
medalla-eth2stats    | standard_init_linux.go:211: exec user process caused "exec format error"

[tzapu]

the magic for the docker builds is in the hooks for docker hub here https://github.com/Alethio/eth2stats-client/pull/36/commits/149e9c35b8468f1ba7f06ef33fd213c368ef8410