updates ci-compile.yml to include LLVM backend

Author: eyck

.github/workflows/ci-compile.yml

@@ -40,10 +40,14 @@ jobs:
           cmake --version
 
       - name: Configure
-        run: cmake --preset Debug -B build -DCMAKE_CXX_STANDARD=${{ matrix.cpp_std }}
+        run: |
+          echo "WITH_LLVM=1" >> $GITHUB_ENV
+          cmake --preset Debug -B build -DCMAKE_CXX_STANDARD=${{ matrix.cpp_std }}
 
       - name: Build
-        run: cmake --build build -j
+        run: |
+          echo "WITH_LLVM=1" >> $GITHUB_ENV
+          cmake --build build -j
 
       - name: Run smoke test
         run: ./build/riscv-sim -h