ci: add ccache hit-rate warning when < 75%

Print the ccache hit-rate for the job using a GitHub annotation if it
was below 75%.

ci/test/03_test_script.sh

@@ -145,6 +145,12 @@ cmake --build "${BASE_BUILD_DIR}" "$MAKEJOBS" --target all $GOAL || (
 )
 
 bash -c "${PRINT_CCACHE_STATISTICS}"
+if [ "$CI" = "true" ]; then
+  hit_rate=$(ccache -s | grep "Hits:" | head -1 | sed 's/.*(\(.*\)%).*/\1/')
+  if [ "${hit_rate%.*}" -lt 75 ]; then
+      echo "::notice title=low ccache hitrate::Ccache hit-rate in $CONTAINER_NAME was $hit_rate%"
+  fi
+fi
 du -sh "${DEPENDS_DIR}"/*/
 du -sh "${PREVIOUS_RELEASES_DIR}"