From b33f9f64c7e7fbc92db2413dcac6f650ddebf80d Mon Sep 17 00:00:00 2001
From: Aiden Grossman <aidengrossman@google.com>
Date: Mon, 28 Jul 2025 12:35:40 -0700
Subject: [PATCH] [libcxx] Enable installing new runner binary on existing
 container

This patch does some refactoring to enable installing a new GHA runner binary
into an existing libcxx image. We achieve this by pushing the base image to the
registry and enabling control over the base image used for building the actions
image. This will always build and push both images even if an existing image is
being used for the actions image, but this should not impact anything as the
SHAs are pinned everywhere and space/build time is not a large concern.

Reviewers: ldionne, EricWF, #reviewers-libcxx

Reviewed By: ldionne

Pull Request: https://github.com/llvm/llvm-project/pull/148073
---
 .github/workflows/libcxx-build-containers.yml |  5 ++++-
 libcxx/utils/ci/Dockerfile                    |  3 ++-
 libcxx/utils/ci/docker-compose.yml            | 11 +++++++++++
 3 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/.github/workflows/libcxx-build-containers.yml b/.github/workflows/libcxx-build-containers.yml
index f432e3ddd5d1..43c446a2c02c 100644
--- a/.github/workflows/libcxx-build-containers.yml
+++ b/.github/workflows/libcxx-build-containers.yml
@@ -34,7 +34,9 @@ jobs:
 
     - name: Build the Linux builder image
       working-directory: libcxx/utils/ci
-      run: docker compose build actions-builder
+      run: |
+        docker compose build builder-base
+        docker compose build actions-builder
       env:
         TAG: ${{ github.sha }}
 
@@ -55,6 +57,7 @@ jobs:
       if: github.event_name == 'push'
       working-directory: libcxx/utils/ci
       run: |
+        docker compose push builder-base
         docker compose push actions-builder
       env:
         TAG: ${{ github.sha }}
diff --git a/libcxx/utils/ci/Dockerfile b/libcxx/utils/ci/Dockerfile
index cec480656c2c..79e11569c0d0 100644
--- a/libcxx/utils/ci/Dockerfile
+++ b/libcxx/utils/ci/Dockerfile
@@ -38,6 +38,7 @@
 # If you're only looking to run the Docker image locally for debugging a
 # build bot, see the `run-buildbot-container` script located in this directory.
 
+ARG ACTIONS_BASE_IMAGE
 
 # HACK: We set the base image in the docker-compose file depending on the final target (buildkite vs github actions).
 # This means we have a much slower container build, but we can use the same Dockerfile for both targets.
@@ -309,7 +310,7 @@ CMD /opt/android/container-setup.sh && buildkite-agent start
 #
 # IMAGE: ghcr.io/libcxx/actions-builder.
 #
-FROM builder-base AS actions-builder
+FROM $ACTIONS_BASE_IMAGE AS actions-builder
 
 ARG GITHUB_RUNNER_VERSION
 
diff --git a/libcxx/utils/ci/docker-compose.yml b/libcxx/utils/ci/docker-compose.yml
index 3b23aa212b6f..36b8dd77c47f 100644
--- a/libcxx/utils/ci/docker-compose.yml
+++ b/libcxx/utils/ci/docker-compose.yml
@@ -3,6 +3,16 @@ x-versions: &compiler_versions
   LLVM_HEAD_VERSION: 21
 
 services:
+  builder-base:
+    image: ghcr.io/llvm/libcxx-linux-builder-base:${TAG}
+    build:
+      context: .
+      dockerfile: Dockerfile
+      target: builder-base
+      args:
+        BASE_IMAGE: ubuntu:jammy
+        <<: *compiler_versions
+
   actions-builder:
     image: ghcr.io/llvm/libcxx-linux-builder:${TAG}
     build:
@@ -11,6 +21,7 @@ services:
       target: actions-builder
       args:
         BASE_IMAGE: ubuntu:jammy
+        ACTIONS_BASE_IMAGE: builder-base
         GITHUB_RUNNER_VERSION: "2.326.0"
         <<: *compiler_versions