.github: update cache key

.github/workflows/macos_build.yml

@@ -31,6 +31,7 @@ jobs:
       # Put ccache into github cache for faster build
       - name: Prepare ccache timestamp
         id: ccache_cache_timestamp
+        shell: bash
         run: |
           NOW=$(date -u +"%F-%T")
           echo "timestamp=${NOW}" >> $GITHUB_OUTPUT

.github/workflows/test_linux_sbc.yml

@@ -57,7 +57,7 @@ jobs:
         with:
           path: ~/.ccache
           key: ${{github.workflow}}-ccache-${{matrix.config}}-${{ matrix.toolchain }}-${{steps.ccache_cache_timestamp.outputs.timestamp}}
-          restore-keys: ${{github.workflow}}-ccache-  # restore ccache from either previous build on this branch or on master
+          restore-keys: ${{github.workflow}}-ccache-${{matrix.config}}-${{ matrix.toolchain }}-  # restore ccache from either previous build on this branch or on master
       - name: setup ccache
         run: |
           . .github/workflows/ccache.env