Experiment with Cirrus cache

.cirrus.yml

@@ -70,11 +70,18 @@ on_failure_template: &ON_FAILURE
 setup_gradle_cache_template: &SETUP_GRADLE_CACHE
   gradle_cache:
     folder: .gradle/caches
-  create_gradle_directory_script:
-    - mkdir -p "${CIRRUS_WORKING_DIR}/.gradle"
+    fingerprint_script: echo "$CIRRUS_BRANCH"
+    reupload_on_changes: "true"
+    populate_script: mkdir -p "${GRADLE_USER_HOME}"
 
 cleanup_gradle_cache_script_template: &CLEANUP_GRADLE_CACHE_SCRIPT
   cleanup_gradle_script:
+    - >
+        for gradle_version in ${GRADLE_USER_HOME}/caches/8.*; do /usr/bin/find $gradle_version -maxdepth 1 -mindepth 1 -type d
+        ! -name "generated-gradle-jars"
+        ! -name "kotlin-dsl"
+        ! -name "scripts"
+        -exec rm -rf {} \;; done
     - rm -rf "${GRADLE_USER_HOME}/caches/journal-1/"
     - find ${GRADLE_USER_HOME}/caches/ -name "*.lock" -type f -delete || true