Fix Ubuntu 20.04 cache keys

Author: MaxDesiatov

.github/workflows/main.yml

@@ -87,9 +87,9 @@ jobs:
       - uses: actions/cache@v1
         with:
           path: ../build-cache
-          key: ${{ runner.os }}-sccache-v10-${{ steps.cache_timestamp.outputs.timestamp }}
+          key: ${{ runner.os }}-sccache-v10-5.3-${{ steps.cache_timestamp.outputs.timestamp }}
           restore-keys: |
-            ${{ runner.os }}-sccache-v10-
+            ${{ runner.os }}-sccache-v10-5.3-
       - name: Build Ubuntu 20.04 installable archive
         run: |
           ./utils/webassembly/ci.sh