x/build/internal/releasetargets: update for each upcoming major Go release

[dmitshur]

At the start of each code freeze, we should evaluate the choice of releaselets (builders that are used for constructing a release artifact) used to make the upcoming major Go release, and confirm they are the most appropriate choice out of what is available.

The start of a code freeze is a safe time to introduce a builder change, as it will be tested during pre-release versions, starting with beta 1 and onwards.

Making this a release blocker for Go 1.16 (and not okay after beta 1—it needs to be done before). Once completed, this issue should be moved to the next major release milestone.

Edit: Starting with Go 1.21, releaselets are only used for running tests. Release artifact construction happens by reproducibly cross-compiling a distpack distribution on a fixed builder.

CC @golang/release, @ianlancetaylor.

[toothrot]

/cc @cagedmantis

[dmitshur]

The @golang/release team has considered the current builders, and we are proposing the following builder changes for the Go 1.16 release:

go1.16*.linux-amd64.tar.gz

	Builder Name	Host Type
Current	linux-amd64-jessie	host-linux-jessie
New	linux-amd64	host-linux-stretch

(Or rather a new builder, identical to the linux-amd64 one, just named linux-amd64-stretch instead.)

Rationale: Debian 8 "Jessie" Long Term Support (LTS) has ended on June 30, 2020 (see https://wiki.debian.org/LTS). We want to start using the next stable release, Debian 9 "Stretch", which has LTS support until June 2022.

Note that this has caused #31293 in April 2019 when this change was made unintentionally as part of a minor release, and it was reverted. We hope that it should be okay to try again for Go 1.16 a year later, since this is being done intentionally this time, and for a major release. CC @ianlancetaylor, @jayconrod, @bradfitz.

go1.16*.linux-386.tar.gz

	Builder Name	Host Type
Current	linux-386	host-linux-jessie
New	linux-386-stretch	host-linux-stretch

Rationale: Same as the one above for linux/amd64.

go1.16*.linux-armv6l.tar.gz

	Builder Name	Host Type
Current	linux-arm	host-linux-arm-scaleway
New	linux-arm-aws	host-linux-arm-aws

Rationale: The replacement builder has proven to be more reliable, and it is easier for us to maintain.

go1.16*.linux-arm64.tar.gz

	Builder Name	Host Type
Current	linux-arm64-packet	host-linux-arm64-packet
New	linux-arm64-aws	host-linux-arm64-aws

Rationale: The replacement builder has proven to be more reliable, and it is easier for us to maintain.

Also see #42304 (comment).

---

Feedback is welcome: we are happy to alter the plan based on information we haven't already considered. These builder changes are planned for Go 1.16 Beta 1, and we will re-evaluate this as needed based on any new findings and feedback.

[gopherbot]

Change https://golang.org/cl/276034 mentions this issue: cmd/release, dashboard: implement builder plan for Go 1.16

[dmitshur]

CL 276034 has implemented the aforementioned plan for Go 1.16.

We'll need to revisit this issue next time during the Go 1.17 development cycle. (If we discover problems with the Go 1.16 plan, we'll come back here, or file new issues.) Moving to the next milestone for now.