ci: shared cache key

.github/workflows/build_all_targets.yml

@@ -13,12 +13,15 @@ jobs:
       options: --user 1000
     outputs:
       matrix: ${{ steps.set-matrix.outputs.matrix }}
+      timestamp: ${{ steps.set-timestamp.outputs.timestamp }}
     steps:
     - uses: actions/checkout@v1
       with:
         token: ${{ secrets.ACCESS_TOKEN }}
     - id: set-matrix
       run: echo "::set-output name=matrix::$(./Tools/generate_board_targets_json.py --group)"
+    - id: set-timestamp
+      run: echo "::set-output name=timestamp::$(date +"%Y%m%d%H%M%S")"
 
   setup:
     name: ${{ matrix.group }}
@@ -37,19 +40,12 @@ jobs:
       # - name: ownership workaround
       #   run: git config --system --add safe.directory '*'
 
-      - name: ccache setup timestamp
-        id: ccache_cache_timestamp
-        shell: cmake -P {0}
-        run: |
-          string(TIMESTAMP current_date "%Y-%m-%d-%H;%M;%S" UTC)
-          message("::set-output name=timestamp::${current_date}")
-
       - name: ccache setup keys
         uses: actions/cache@v2
         with:
           path: ~/.ccache
-          key: ${{ matrix.arch }}-ccache-${{ steps.ccache_cache_timestamp.outputs.timestamp }}
-          restore-keys: ${{ matrix.arch }}-ccache-
+          key: ${{ matrix.arch }}-ccache-${{ needs.group_targets.outputs.timestamp }}
+          restore-keys: ${{ matrix.arch }}-ccache-${{ needs.group_targets.outputs.timestamp }}
 
       - name: setup ccache
         run: |