workflow: print compiler cache statistics after building firmware

Print the compiler cache (ccache) statistics after building the
firmware to aid in future debugging.

Co-authored-by: Fabio Baltieri <fabiobaltieri@google.com>
Signed-off-by: Henrik Brix Andersen <henrik@brixandersen.dk>

Author: henrikbrixandersen

.github/workflows/test.yaml

@@ -65,3 +65,8 @@ jobs:
           PLATFORMS_FLAGS+="-p qemu_x86_64"
 
           ./scripts/twister --force-color --inline-logs -T samples/hello_world -v $PLATFORMS_FLAGS $EXTRA_TWISTER_FLAGS
+
+      - name: Print ccache stats
+        if: runner.os != 'Windows'
+        run: |
+          ccache -s -vv