Add linux/arm64 to nightly, make it multiplatform

[wallyqs]

Makes nightly multi platform and add support for arm64 which we use more in testing lately.

Generates:

• Single

  • synadia/nats-server:nightly-amd64
  • synadia/nats-server:nightly-arm64
  • synadia/nats-server:nightly-20250905-amd64
  • synadia/nats-server:nightly-20250905-arm64

• Multi

  • synadia/nats-server:nightly (both amd64 and arm64)
  • synadia/nats-server:nightly-20250905

Signed-off-by: Waldemar Quevedo wally@nats.io

[samuelattwood]

LGTM

[neilalexander]

I'm fine with adding the ARM64 builds but I don't see much use in the -amd64 and -arm64 tag prefixes, Docker should only pull the right layers for the right architecture regardless.

[philpennock]

There's a choice. We can switch to requiring the newest GoReleaser and drop the need for the -{platform_arch} suffices, or we can accept that this works as-is and seems to be based on the well-tested flow used for Synadia's commercial builds for some time and which the open source project is welcome to use.

I think this is fine as-is, but we should plan on trying out the new GoReleaser functionality "sometime soon". We don't guarantee the availability of the platform variants, it's an implementation detail and we can freely withdraw it. If it breaks for someone, they were doing something silly with open source and we're not obligated to support them.

So I'm approving as-is, but won't object to changes to avoid the arch.

[neilalexander]

I would prefer we get multi-arch images right rather than having new suffixes and breaking an established naming convention.

[samuelattwood]

In my view this doesn't break established naming, the multi-arch manifest remains and is how this will typically be pulled, it just also gives a tag to the underlying SHAs that the manifest references. This is a pretty typical approach with GoReleaser.