Dev workflow: add building for ARM platforms

[kdavis]

Related to #1093

I missed the change for the dev workflow, so hopefully builds in https://hub.docker.com/r/squidex/squidex/tags will also be arm64 too

[SebastianStehle]

I think I have to revert that. The build fails all the time now.

[SebastianStehle]

Btw: Why do you build twice?

[kdavis]

@SebastianStehle If you revert, you'll also need to revert #1093 (as that will have a similar issue)

I built twice as this commit 2642d0a specifies multiple build platforms whilst also having a load: true (which conflicts when trying to build). In the second build, I run the same params again with multiple build platforms, but without the load: true

In retrospect, it'd probably be easier to just have a matrix with the build platforms... 🤔

[SebastianStehle]

I have solved it by adding the cleanup step: https://github.com/Squidex/squidex/blob/master/.github/workflows/release.yml#L119

Matrix build would also run the tests twice I guess, so your approach is probably better.