feat(build): centralize LLVM_VERSION

[reneleonhardt]

Features

• Centralized the diverged LLVM_VERSION in docker / non-docker builds
• Folded the higher number from non-docker 20.1.3 (latest is 20.1.7)
• Prepared the renovate comment if updates would be allowed in .github/renovate.json5

Working example

https://docs.renovatebot.com/modules/manager/regex/#regular-expression-capture-groups

{
  "customManagers": [
    {
      "description": "Update _VERSION in ci scripts",
      "customType": "regex",
      "managerFilePatterns": ["src/ci/**/*.sh"],
      "matchStrings": [
        "# renovate: datasource=(?<datasource>.*?) depName=(?<depName>\\S+)( versioning=(?<versioning>\\S+))?( extractVersion=(?<extractVersion>\\S+))?[^\\n]*\\nexport .+_VERSION=(?<currentValue>\\S+)",
      ],
      "versioningTemplate": "{{#if versioning}}{{{versioning}}}{{else}}semver-coerced{{/if}}",
    },
  ],
}

[rustbot]

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[bjorn3]

This should not be automatically updated I think. LLVM updates are more risky than regular dependency updates and frequently need changes on the rust side.

[reneleonhardt]

renovate doesn't merge automatically, maintainers would still have to do that manually like for dependabot.

For what it's worth, you saw that I didn't enable the regex customManager for these lines in renovate.json5...

[bjorn3]

Maybe put this in shared.sh instead?

[reneleonhardt]

Would be possible of course.

I didn't know if all those functions would be unwanted in the non-docker builds, that's why I separated the shared versions from shared functions...

[nikic]

These versions should not be shared. There is little value in keeping them exactly synchronized, and the process for updating them is quite different. One of them is just built in CI, while the other requires uploading new artifacts via ci-mirrors.

[reneleonhardt]

These versions should not be shared. There is little value in keeping them exactly synchronized, and the process for updating them is quite different. One of them is just built in CI, while the other requires uploading new artifacts via ci-mirrors.

There was no comment explaining why non-docker would need the outdated 20.1.0-rc2 instead of 20.1.0-rc3 or a stable release like in docker builds (20.1.3).
There were these comments in both files as you can see in the diff:

# Try to keep the LLVM version here in sync with src/ci/scripts/install-clang.sh
# Try to keep this in sync with src/ci/docker/scripts/build-clang.sh

If both comments have been wrong, please clarify them and upgrade both scripts separately.

You would still be able to enable renovate to update both separately and benefit from automatic CI builds for docker and non-docker to see if a new release is compatible respectively brings no regression for one of them.

[Kobzol]

The comment isn't wrong per-se, it just maybe could be clarified a bit. Normally we would say something like "WARNING: KEEP IN SYNC WITH X" if it was really required. Here it's more like "when you bump the Linux version, try to think of also updating the Windows/MacOS version sometime in the near-ish future, just to make sure that these versions don't diverge by 5 years.. again :D".

Happy to review clarification of the comments. We don't need renovatebot here though.