CI: Be a bit less paranoid about old compiler versions existing

We explicitly tell CMake what compiler to use. No need to remove older
versions, which was just one extra thing we needed to maintain.

.github/actions/setup/action.yml

@@ -22,7 +22,6 @@ runs:
         # Packages below aren't.
 
         set -e
-        sudo apt-get purge -y clang-13 clang-14 clang-15 gcc-10 gcc-11 gcc-12
 
         wget -O - https://apt.llvm.org/llvm-snapshot.gpg.key | sudo apt-key add -
         sudo add-apt-repository 'deb http://apt.llvm.org/jammy/ llvm-toolchain-jammy-18 main'

.github/workflows/lagom-template.yml

@@ -115,8 +115,8 @@ jobs:
             -DENABLE_FUZZERS_LIBFUZZER=ON \
             -DENABLE_ADDRESS_SANITIZER=ON \
             -DSERENITY_CACHE_DIR=${{ github.workspace }}/Build/caches \
-            -DCMAKE_C_COMPILER=clang \
-            -DCMAKE_CXX_COMPILER=clang++ \
+            -DCMAKE_C_COMPILER=${{ steps.build-parameters.outputs.host_cc }} \
+            -DCMAKE_CXX_COMPILER=${{ steps.build-parameters.outputs.host_cxx }} \
             -DCMAKE_PREFIX_PATH=tool-install
 
       # === BUILD ===