Try to use newer clang to prevent internal compiler error with clang-20 in release mode

Author: fabianbs96

.github/workflows/ci.yml

@@ -15,7 +15,7 @@ jobs:
       fail-fast: true
       matrix:
         os: [ubuntu-24.04, ubuntu-24.04-arm]
-        compiler: [ [clang++-20, clang-20, "clang-20 libclang-rt-20-dev clang-tools-20"] ]
+        compiler: [ [clang++-21, clang-21, "clang-21 libclang-rt-21-dev clang-tools-21"] ]
         build: [ Debug, Release, DebugLibdeps, DebugCov ]
         llvm-version: [ 16, "22.1" ]
         include:
@@ -31,7 +31,7 @@ jobs:
           - build: DebugCov
             cmake_build_type: Debug
             flags: -DCODE_COVERAGE=ON
-            extra_dependencies: llvm-20 # For coverage
+            extra_dependencies: llvm-21 # For coverage
           - llvm-version: 16
             llvm-major-version: 16
           - llvm-version: "22.1"