WIP: Added Docker multiarch build

[GeorgeSapkin]

This is a work in progress of a Docker multiarch build. arm64v8 seems to be broken ATM. qemu-user-static needs to be setup for this to work.

Usage

Build operator:

make operator repo=somedockerid

This will make ${somedockerid}/nats-operator/${arch}-${git_tag} images.

Push operator and multiarch manifest:

make push-operator repo=somedockerid

Same commands are available for reloader.

Only amd64 and arm32v6 are tested and working when building from Fedora 28 x64 with Docker 18.06.0-ce and QEMU 2.11.2-2.fc28.

TODO:

• Fix arm64v8 build. Currently it's giving me:

go tool link: exit status 127
**
ERROR:/builddir/build/BUILD/qemu-2.11.2/qom/object.c:1645:object_get_canonical_path_component: code should not be reached