Add dummy CUDA CI test.

.github/workflows/main.yml

@@ -87,6 +87,25 @@ jobs:
     - run: cargo test ${{ matrix.no_run }} --manifest-path cc-test/Cargo.toml --target ${{ matrix.target }} --features parallel
     - run: cargo test ${{ matrix.no_run }} --manifest-path cc-test/Cargo.toml --target ${{ matrix.target }} --release
 
+  cuda:
+    name: Test CUDA support
+    runs-on: ubuntu-20.04
+    steps:
+    - uses: actions/checkout@master
+    - name: Install cuda-minimal-build-11-4
+      shell: bash
+      run: |
+        # https://developer.nvidia.com/cuda-downloads?target_os=Linux&target_arch=x86_64&Distribution=Ubuntu&target_version=20.04&target_type=deb_network
+        wget https://developer.download.nvidia.com/compute/cuda/repos/ubuntu2004/x86_64/cuda-ubuntu2004.pin
+        sudo mv cuda-ubuntu2004.pin /etc/apt/preferences.d/cuda-repository-pin-600
+        sudo apt-key adv --fetch-keys https://developer.download.nvidia.com/compute/cuda/repos/ubuntu2004/x86_64/7fa2af80.pub
+        sudo add-apt-repository "deb https://developer.download.nvidia.com/compute/cuda/repos/ubuntu2004/x86_64/ /"
+        sudo apt-get update
+        sudo apt-get -y install cuda-minimal-build-11-4
+    - name: Test 'cudart' feature
+      shell: bash
+      run: env PATH=/usr/local/cuda/bin:$PATH cargo test --manifest-path cc-test/Cargo.toml --features test_cuda
+
   msrv:
     name: MSRV
     runs-on: ${{ matrix.os }}