doc, x/build/dashboard: document Go 1.16 requires at least OpenBSD 6.4, drop OpenBSD 6.2 builders

[dmitshur]

Based on investigation and discussion in #42237 and #42408, and past support policy discussion in #15227 (comment), we should drop OpenBSD 6.2 support from the upcoming Go 1.16 release. What's needed:

• Disable openbsd-{386,amd64}-62 builders for Go 1.16 and newer.
• Document in Go 1.16 release notes that Go 1.16 requires at least OpenBSD 6.4: "Go 1.15 was the last release that ran on OpenBSD 6.2. Go 1.16 requires OpenBSD 6.4 or newer."
  • Ideally we should say OpenBSD 6.7 or newer, but we don't have builders to back up such a claim (see x/build/env/openbsd: add OpenBSD 6.8 builder #35712), so I think this is the best we can say for now.
  • Ideally we would've pre-announced this earlier, like in Go 1.11 release notes. Unfortunately we didn't have the information we have now earlier.
  • This became unneeded because we were able to add an OpenBSD 6.8 builder and get it passing in time.
• Update relevant golang.org/wiki pages as needed.

Please comment if you think this plan can be improved.

CC @golang/release, @ianlancetaylor, @4a6f656c, @prattmic, @bcmills.

[gopherbot]

Change https://golang.org/cl/268097 mentions this issue: cmd/dist: skip static testtls on OpenBSD 6.2 and earlier

[dmitshur]

There seems to be agreement to move forward with this plan, so moving this issue to NeedsFix.

[gopherbot]

Change https://golang.org/cl/268880 mentions this issue: dashboard: only run openbsd-{386,amd64}-62 builders on Go 1.15 and older