Use a matrix for nightly valgrind (Take 1)

.github/workflows/nightly.yml

@@ -149,20 +149,31 @@ jobs:
 
   valgrind:
     name: "valgrind"
+    strategy:
+      fail-fast: false
+
+      matrix:
+        compiler: [clang, gcc]
+        cxxflags: ["-O0", "-O1", "-O2", "-O3", "-Os"]
 
     runs-on: ubuntu-24.04
 
     steps:
       - uses: actions/checkout@v4
 
+      - name: Create Cache Key Hash
+        run: |
+          hash=$(echo "${{ matrix.compiler }}${{ matrix.cxxflags }}" | sha256sum | head -c 10)
+          echo "CACHE_KEY_HASH=${hash}" >> $GITHUB_ENV
+
       - name: Setup Build Agent
         uses: ./.github/actions/setup-build-agent
         with:
           target: valgrind-full
-          cache-key: linux-x86_64-valgrind-full
+          cache-key: linux-x86_64-valgrind-full-${{ env.CACHE_KEY_HASH }}
 
       - name: Valgrind Checks
-        run: python3 ./src/scripts/ci_build.py --cc=clang --make-tool=make valgrind-full
+        run: python3 ./src/scripts/ci_build.py --make-tool=ninja --cc=${{ matrix.compiler }} --extra-cxxflags="${{ matrix.cxxflags }}" valgrind-full
 
   hybrid_tls_interop:
     name: "PQ/T TLS 1.3"