From f9a05e755473e1481cd8c5c32eeb67e61625bbed Mon Sep 17 00:00:00 2001
From: Dirk Stolle <striezel-dev@web.de>
Date: Sun, 1 Jun 2025 07:14:14 +0200
Subject: [PATCH] ci: move Ubuntu 20.04 builds to container

The Ubuntu 20.04 image on GitHub Actions has been unavailable since
2025-04-15. See <https://github.com/actions/runner-images/issues/11101>
for more information on the deprecation and removal.

Therefore all build jobs that use the Ubuntu 20.04 runner image
of GHA have to be moved to Docker containers using Ubuntu 20.04.
---
 .github/workflows/ci.yml | 33 +++++++++++++++++++++++----------
 1 file changed, 23 insertions(+), 10 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 5bec173..07cf959 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -33,14 +33,17 @@ jobs:
             container: ubuntu:18.04
           - toolset: gcc-8
             cxxstd: "11,14,17,2a"
-            os: ubuntu-20.04
+            os: ubuntu-latest
+            container: ubuntu:20.04
             install: g++-8
           - toolset: gcc-9
             cxxstd: "11,14,17,2a"
-            os: ubuntu-20.04
+            os: ubuntu-latest
+            container: ubuntu:20.04
           - toolset: gcc-10
             cxxstd: "11,14,17,2a"
-            os: ubuntu-20.04
+            os: ubuntu-latest
+            container: ubuntu:20.04
             install: g++-10
           - toolset: gcc-11
             cxxstd: "11,14,17,20"
@@ -80,35 +83,45 @@ jobs:
           - toolset: clang
             compiler: clang++-6.0
             cxxstd: "11,14,17"
-            os: ubuntu-20.04
+            os: ubuntu-latest
+            container: ubuntu:20.04
             install: clang-6.0
           - toolset: clang
             compiler: clang++-7
             cxxstd: "11,14,17"
-            os: ubuntu-20.04
+            os: ubuntu-latest
+            container: ubuntu:20.04
             install: clang-7
           - toolset: clang
             compiler: clang++-8
             cxxstd: "11,14,17"
-            os: ubuntu-20.04
+            os: ubuntu-latest
+            container: ubuntu:20.04
             install: clang-8
           - toolset: clang
             compiler: clang++-9
             cxxstd: "11,14,17"
-            os: ubuntu-20.04
+            os: ubuntu-latest
+            container: ubuntu:20.04
             install: clang-9
           - toolset: clang
             compiler: clang++-10
             cxxstd: "11,14,17,2a"
-            os: ubuntu-20.04
+            os: ubuntu-latest
+            container: ubuntu:20.04
+            install: clang-10
           - toolset: clang
             compiler: clang++-11
             cxxstd: "11,14,17,2a"
-            os: ubuntu-20.04
+            os: ubuntu-latest
+            container: ubuntu:20.04
+            install: clang-11
           - toolset: clang
             compiler: clang++-12
             cxxstd: "11,14,17,20"
-            os: ubuntu-20.04
+            os: ubuntu-latest
+            container: ubuntu:20.04
+            install: clang-12
           - toolset: clang
             compiler: clang++-13
             cxxstd: "11,14,17,20,2b"