Attempt to fix the CI by installing clang-19

Author: antoyo

.github/workflows/ci.yaml

@@ -115,6 +115,9 @@ jobs:
       - if: matrix.backend == 'gcc'
         run: |
           sudo apt-get -y --no-install-recommends purge cpp gcc
+          sudo apt-get install clang-19
+          sudo update-alternatives --install /usr/bin/clang clang /usr/bin/clang-19 190
+
           curl --proto '=https' --tlsv1.2 -sSfLO https://github.com/rust-lang/gcc/releases/latest/download/gcc-15.deb
           sudo dpkg -i gcc-15.deb