CI: Work around Clang pipelines breakage in GHA

See actions/runner-images#8659

.github/workflows/ci.yml

@@ -94,10 +94,14 @@ jobs:
  tools: "tools_ninja${{ startsWith(matrix.os, 'windows') && ' tools_opensslv3_x64' || '' }}"
 
  # Install on Linux via apt to get Qt built with OpenSSL 3
- - name: Install Qt (Linux)
+ - name: Install dependencies (Linux)
  if: startsWith(matrix.os, 'ubuntu')
  run: |
  COMMON_PKGS="libolm-dev ninja-build"
+ # Workaround for https://github.com/actions/runner-images/issues/8659
+ sudo rm -f /etc/apt/sources.list.d/ubuntu-toolchain-r-ubuntu-test-jammy.list
+ COMMON_PKGS="--allow-downgrades libc6=2.35-0ubuntu3.4 libc6-dev=2.35-0ubuntu3.4 libstdc++6=12.3.0-1ubuntu1~22.04 libgcc-s1=12.3.0-1ubuntu1~22.04 $COMMON_PKGS"
+ # End of workaround
  sudo apt-get -qq update
  sudo apt-get -qq install $COMMON_PKGS \
  ${{ matrix.qt-version == 5