Added mtime wd

Author: bathal1

.github/workflows/build_mitsuba_ubuntu/action.yml

@@ -33,7 +33,11 @@ runs:
       submodules: recursive
       fetch-depth: 0
 
-  - uses: chetan/git-restore-mtime-action@v2
+  - name: Restore timestamps 
+    uses: chetan/git-restore-mtime-action@v2
+    with:
+      working-directory: mitsuba3
+
 
   - name: Build Mitsuba 3
     shell: bash