ci: llvm-20

Author: yamt

.github/workflows/ci.yml

@@ -411,7 +411,7 @@ jobs:
       if: startsWith(matrix.os, 'ubuntu-') && matrix.arch == 'native'
       run: |
         sudo ./cross/setup-apt-llvm-org.sh
-        sudo apt-get update && sudo apt-get install -y clang-18 lld-18
+        sudo apt-get update && sudo apt-get install -y clang-20 lld-20
         sudo ./cross/setup-alternatives.sh
 
     - name: Fix sources.list (cross)