fix(ci): Keep LLVM apt setup for clang/lld/lldb, use pip for clang-format

Restore the apt LLVM v20 installation for clang, lld, and lldb (needed
for native builds) and install clang-format v22 separately via pip
since apt.llvm.org doesn't have v22 packages yet.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: antonis

.github/workflows/buildandtest.yml

@@ -51,7 +51,20 @@ jobs:
       - name: Install Dependencies
         run: yarn install
 
-      - name: Setup clang-format
+      # Default of ubuntu and apt packages are too old compared to macos packages.
+      # This is required for using a newer version of clang-format.
+      - name: Setup clang V20
+        run: |
+          sudo bash -c "$(wget -O - https://apt.llvm.org/llvm.sh)" 20
+          sudo apt-get install -y clang-20 lld-20 lldb-20
+
+      - name: Set clang V20 as default
+        run: |
+          sudo update-alternatives --install /usr/bin/clang clang /usr/bin/clang-20 200
+          sudo update-alternatives --install /usr/bin/clang++ clang++ /usr/bin/clang++-20 200
+          clang --version
+
+      - name: Setup clang-format V22
         run: |
           pip install --break-system-packages clang-format==22.1.2
           clang-format --version