Update code base to use LLVM 21 (#434)

Signed-off-by: Cyrill Leutwiler <bigcyrill@hotmail.com>
Co-authored-by: LJ <81748770+elle-j@users.noreply.github.com>
Co-authored-by: xermicus <cyrill@parity.io>

.github/workflows/benchmark.yml

@@ -60,7 +60,7 @@ jobs:
 
       - name: Set LLVM Environment Variables
         run: |
-          echo "LLVM_SYS_181_PREFIX=$(pwd)/llvm-x86_64-unknown-linux-gnu" >> $GITHUB_ENV
+          echo "LLVM_SYS_211_PREFIX=$(pwd)/llvm-x86_64-unknown-linux-gnu" >> $GITHUB_ENV
 
       - name: Build resolc
         run: |