CI: Build binaries for all platforms supported by golang
There are several targets we could support but don't at the moment, such as
- darwin/x86
- darwin/amd64
- freebsd/amd64
- ...
I think we have enough computing resources to create builds for all supported platforms, even if we will not be able to test all of them. (Maybe adding flags to untested builds such as untested
would be a good idea also)