[llvm] [libc++] Add Docker images to support incoming pre-merge CI transition (PR #144597)

[Louis Dionne via llvm-commits]

https://github.com/ldionne created https://github.com/llvm/llvm-project/pull/144597

As described in [1], we are transitioning to the LLVM-wide pre-merge CI infrastructure. As part of this change, we need a way to specify which Docker image to use from the sources, and we can't do that from the workflow files directly due to a Kubernetes bug. Instead, the runner groups are going to pick up the Docker image specified in this json file as it appears on the `main` branch of the official LLVM Github repository.

[1]: https://discourse.llvm.org/t/rfc-migrating-libc-premerge-testing-to-new-llvm-premerge-testing-infrastructure

>From 6da10f660e2728a086d25673cf172b26519f8824 Mon Sep 17 00:00:00 2001
From: Louis Dionne <ldionne.2 at gmail.com>
Date: Tue, 17 Jun 2025 16:18:12 -0400
Subject: [PATCH] [libc++] Add Docker images to support incoming pre-merge CI
 transition

As described in [1], we are transitioning to the LLVM-wide pre-merge
CI infrastructure. As part of this change, we need a way to specify
which Docker image to use from the sources, and we can't do that from
the workflow files directly due to a Kubernetes bug. Instead, the runner
groups are going to pick up the Docker image specified in this json file
as it appears on the `main` branch of the official LLVM Github repository.

[1]: https://discourse.llvm.org/t/rfc-migrating-libc-premerge-testing-to-new-llvm-premerge-testing-infrastructure
---
 .github/workflows/libcxx-docker-images.yml | 12 ++++++++++++
 1 file changed, 12 insertions(+)
 create mode 100644 .github/workflows/libcxx-docker-images.yml

diff --git a/.github/workflows/libcxx-docker-images.yml b/.github/workflows/libcxx-docker-images.yml
new file mode 100644
index 0000000000000..9366d825ba415
--- /dev/null
+++ b/.github/workflows/libcxx-docker-images.yml
@@ -0,0 +1,12 @@
+# This file defines the Docker images used by various self-hosted runner groups used
+# in the libc++ pre-merge testing pipeline.
+#
+# The images are specified this way instead of being in the workflow file due to a
+# Kubernetes bug, as described in https://discourse.llvm.org/t/rfc-migrating-libc-premerge-testing-to-new-llvm-premerge-testing-infrastructure.
+#
+# When updating this file, the self-hosted runner sets are going to pick up the
+# specified image after a short delay. The Docker images used are always the
+# ones on the 'main' branch of the official LLVM GitHub repository.
+libcxx-runner-set-current: ghcr.io/llvm/libcxx-linux-builder:b060022103f551d8ca1dad84122ef73927c86512
+libcxx-runner-set-next: none
+libcxx-runner-set-release: ghcr.io/llvm/libcxx-linux-builder:d8a0709b1090350a7fe3604d8ab78c7d62f10698