Limit Docker tests to Linux

Author: s1hofmann

.github/workflows/snapshot.yaml

@@ -63,6 +63,7 @@ jobs:
         with:
           node-version: 14
       - name: Setup Docker
+        if: ${{matrix.os === 'ubuntu-latest'}}
         run: |
           docker pull s1hofmann/nut-ci:latest
           docker run -it -d --name nut-ci --shm-size 4gb --user $(id -u):$(id -g) -v ${PWD}:${PWD}:rw s1hofmann/nut-ci:latest bash
@@ -77,6 +78,7 @@ jobs:
         with:
           run: npm run coverage -- --coverageDirectory=coverage/unit
       - name: Run Docker E2E tests
+        if: ${{matrix.os === 'ubuntu-latest'}}
         run: docker exec nut-ci bash -c "bash $PWD/.build/build.sh ${PWD} 14"
 
   deploy: