}

        return Optional.of(Instant.ofEpochMilli(gcFile.lastModified()));
    }

    private static class CacheCleanupDetails implements CacheCleanupBuildOperationType.Details {
        private final File cacheLocation;

        public CacheCleanupDetails(File cacheLocation) {
            this.cacheLocation = cacheLocation;
        }

        @Override
        public File getCacheLocation() {