Go: x/build/cmd/releasebot: provide binary release for darwin/arm64 for 1.16

[dmitshur]

Based on discussion in a release meeting, I understand our current plan is to aim to provide binaries (and installer) for darwin/arm64 in time for the Go 1.16 release.

I'm making this as the tracking issue which reflects the current state: there are release-blocker, NeedsInvestigation, okay-after-beta1 labels applied, and the Go1.16 milestone set. Perhaps this will need to change as time passes.

Ideally, this will be implemented by using a darwin/arm64 builder (issue #39782) if that builder becomes available soon. If that builder cannot be added in time, we may need to implement this via a temporary workaround.

CC @golang/release, @cherrymui, @aclements, @FiloSottile, @rsc.

[dmitshur]

Our recently-updated plan here is to try to get this in before beta 1 this week. Removing okay-after-beta1 to reflect that status.

[gopherbot]

Change https://golang.org/cl/278435 mentions this issue: cmd/release: set macOS deployment target for darwin/arm64 too

[gopherbot]

Change https://golang.org/cl/278436 mentions this issue: cmd/release: add darwin-arm64 target

[gopherbot]

Change https://golang.org/cl/278772 mentions this issue: dashboard: remove known issue for darwin arm builder

[dmitshur]

With issue #39782 being resolved now, CL 278436, and additional internal release workflow changes to codesign and notarize macOS binaries, and testing, the work needed be able to provide a binary release for the new darwin/arm64 port has been done.

The upcoming Go 1.16 Beta 1 release and further Go 1.16 releases will have go*.darwin-arm64.pkg installer and go*.darwin-arm64.tar.gz archive files provided at https://golang.org/dl/. Closing.

[gopherbot]

Change https://golang.org/cl/278787 mentions this issue: internal/dl: categorize new darwin/arm64 binaries better