[llvm] Update actions/checkout action to v6 (PR #171065)

[Mend Renovate via llvm-commits]

https://github.com/renovate-bot created https://github.com/llvm/llvm-project/pull/171065

This PR contains the following updates:

| Package | Type | Update | Change |
|---|---|---|---|
| [actions/checkout](https://redirect.github.com/actions/checkout) | action | major | `v5.0.0` -> `v6.0.1` |

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> [!WARNING]
> Some dependencies could not be looked up. Check the Dependency Dashboard for more information.

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### Release Notes

<details>
<summary>actions/checkout (actions/checkout)</summary>

### [`v6.0.1`](https://redirect.github.com/actions/checkout/compare/v6.0.0...v6.0.1)

[Compare Source](https://redirect.github.com/actions/checkout/compare/v6.0.0...v6.0.1)

### [`v6.0.0`](https://redirect.github.com/actions/checkout/compare/v5.0.1...v6.0.0)

[Compare Source](https://redirect.github.com/actions/checkout/compare/v5.0.1...v6.0.0)

### [`v5.0.1`](https://redirect.github.com/actions/checkout/releases/tag/v5.0.1)

[Compare Source](https://redirect.github.com/actions/checkout/compare/v5.0.0...v5.0.1)

##### What's Changed

- Port v6 cleanup to v5 by [@​ericsciple](https://redirect.github.com/ericsciple) in [#​2301](https://redirect.github.com/actions/checkout/pull/2301)

**Full Changelog**: <https://github.com/actions/checkout/compare/v5...v5.0.1>

</details>

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🔕 **Ignore**: Close this PR and you won't be reminded about this update again.

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>From 40f954e6b0af623f475d4e64d6abb615941991e3 Mon Sep 17 00:00:00 2001
From: Mend Renovate <bot at renovateapp.com>
Date: Mon, 8 Dec 2025 00:03:09 +0000
Subject: [PATCH] Update actions/checkout action to v6

---
 .github/workflows/release-sources.yml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.github/workflows/release-sources.yml b/.github/workflows/release-sources.yml
index 20e7c62976098..ea6a81c8c7b95 100644
--- a/.github/workflows/release-sources.yml
+++ b/.github/workflows/release-sources.yml
@@ -108,7 +108,7 @@ jobs:
       attestations: write
     steps:
       - name: Checkout Release Scripts
-        uses: actions/checkout at 08c6903cd8c0fde910a37f88322edcfb5dd907a8 # v5.0.0
+        uses: actions/checkout at 8e8c483db84b4bee98b60c0593521ed34d9990e8 # v6.0.1
         with:
           sparse-checkout: |
             .github/workflows/upload-release-artifact