Bump actions/cache from 2.1.6 to 2.1.7

Bumps [actions/cache](https://github.com/actions/cache) from 2.1.6 to 2.1.7.
- [Release notes](https://github.com/actions/cache/releases)
- [Commits](https://github.com/actions/cache/compare/v2.1.6...v2.1.7)

---
updated-dependencies:
- dependency-name: actions/cache
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

.github/workflows/linux-workflow.yml

@@ -118,7 +118,7 @@ jobs:
           message("::set-output name=timestamp::${current_date}")
 
       - name: ccache cache files
-        uses: actions/cache@v2.1.6
+        uses: actions/cache@v2.1.7
         with:
           path: .ccache
           key: ${{ matrix.os }} ${{ matrix.platform }} ${{ matrix.compiler }}${{ matrix.detail }} ccache ${{ steps.ccache_cache_timestamp.outputs.timestamp }}