Use tar to preserve links

Something broke in the actions/download-artifact action and it is not preserving symbolic links. It didn't get a new release so my guess is that something was updated in the node environment or in npm. This is a future proof solution to preserve the fs structure between upload and download.

.github/workflows/openvpn.yml

@@ -27,11 +27,14 @@ jobs:
           configure: --enable-openvpn
           install: true
 
+      - name: tar build-dir
+        run: tar -zcf build-dir.tgz build-dir
+
       - name: Upload built lib
         uses: actions/upload-artifact@v4
         with:
           name: wolf-install-openvpn
-          path: build-dir
+          path: build-dir.tgz
           retention-days: 5
 
   openvpn_check:
@@ -50,7 +53,9 @@ jobs:
         uses: actions/download-artifact@v4
         with:
           name: wolf-install-openvpn
-          path: build-dir
+
+      - name: untar build-dir
+        run: tar -xf build-dir.tgz
 
       - name: Install dependencies
         run: |