Add a CircleCI job to test oqs-provider against memory leaks.

This commit introduces a new CircleCI job called `check-ASan-tests` that compiles
OpenSSL 3, liboqs and oqs-provider with ASan (`-fsanitize=address`). Then, it
runs the CTest suite.

If any memory leak occurs somewhere and is triggered in one of the various unit tests,
then this CircleCI job fails and displays the ASan trace.

.github/workflows/asan.yml

@@ -0,0 +1,80 @@
+name: ASan tests
+
+on:
+  push:
+    branches: [ '*' ]
+  pull_request:
+    branches: [ "main" ]
+
+jobs:
+
+  asan_linux_intel:
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+    container:
+      image: openquantumsafe/ci-ubuntu-jammy:latest
+    env:
+      CC: "clang"
+      CXX: "clang++"
+      ASAN_C_FLAGS: "-fsanitize=address -fno-omit-frame-pointer"
+      ASAN_OPTIONS: "detect_stack_use_after_return=1,detect_leaks=1"
+      OPENSSL_BRANCH: "openssl-3.1"
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v2
+
+      - name: Install dependencies
+        run: apt-get update && apt-get install -y clang llvm ninja-build git cmake libclang-rt-14-dev libclang-common-14-dev
+
+      - name: Clone and build OpenSSL(3) with ASan
+        run: |
+          git clone --depth=1 --branch "${OPENSSL_BRANCH}" https://github.com/openssl/openssl.git openssl
+          cd openssl
+          mkdir install
+          ./Configure --openssldir="${PWD}/install" \
+                      --prefix="${PWD}/install" \
+                      --debug \
+                      enable-asan \
+                      no-tests
+          make -j$(nproc)
+          make install_sw
+          cd ..
+
+      - name: Clone and build liboqs with ASan
+        run: |
+          git clone --depth=1 --branch main https://github.com/open-quantum-safe/liboqs.git liboqs
+          cd liboqs
+          mkdir build install
+          cmake -GNinja -B build \
+                -DCMAKE_BUILD_TYPE=Debug \
+                -DOQS_USE_OPENSSL=OFF \
+                -DCMAKE_C_FLAGS="${ASAN_C_FLAGS}" \
+                -DCMAKE_EXE_LINKER_FLAGS="${ASAN_C_FLAGS}" \
+                -DCMAKE_INSTALL_PREFIX="${PWD}/install"
+          cmake --build build -j$(nproc)
+          cmake --install build
+          cd ..
+
+      - name: Build oqs-provider with ASan
+        run: |
+          cmake -GNinja -B build \
+                -DCMAKE_BUILD_TYPE=Debug \
+                -DOPENSSL_ROOT_DIR="$PWD/openssl/install" \
+                -Dliboqs_DIR="$PWD/liboqs/install/lib/cmake/liboqs" \
+                -DCMAKE_C_FLAGS="${ASAN_C_FLAGS}" \
+                -DCMAKE_EXE_LINKER_FLAGS="${ASAN_C_FLAGS}"
+          cmake --build build -j$(nproc)
+
+      - name: Verify that test binaries are linked against ASan
+        run: |
+          find build/test/ -type f -perm '/u=x' | while read -r test_bin; do
+            if ! nm "${test_bin}" | grep -q '__local_asan_preinit'; then
+              echo "ASan not found in ${test_bin}"
+              exit 1
+            fi
+          done
+
+      - name: Run tests
+        run: ctest --test-dir build --output-on-failure
+