Upload vsix only in ubuntu

Author: jneira

.github/workflows/test.yml

@@ -23,7 +23,7 @@ jobs:
       - name: Install Node.js
         uses: actions/setup-node@v1
         with:
-          node-version: 10.x
+          node-version: 12
       - name: Ensure there is a supported ghc versions
         uses: haskell/actions/setup@v1
         with:
@@ -41,8 +41,10 @@ jobs:
           name: extension-${{ matrix.os }}.log
           path: test-workspace/hls.log
       - name: Package tested extension
+        if: runner.os == 'Linux'
         run: vsce package
       - name: Upload extension vsix to workflow artifacts
+        if: runner.os == 'Linux'
         uses: actions/upload-artifact@v2
         with:
           name: haskell-${{ github.sha }}.vsix