build artifact for debugging

Author: wjakob

.github/workflows/build.yml

@@ -44,6 +44,11 @@ jobs:
         run: |
           cmake --build build --config Release --parallel
 
+      - uses: actions/upload-artifact@v2
+        with:
+          name: mitsuba2-next-win64.zip
+          path: build/Release/
+
       - name: Run test suite
         run: |
           cd build/Release