Add log for lib path

[SidneyLann]

When downloading lib files to .djl.ai, the downloading always block, I need to download manually and put them to the correct path. in LibUtils.java, suggest add log like below:

private static Path findJniLibrary(LibTorch libTorch) {
String classifier = libTorch.classifier;
String version = libTorch.version;
String djlVersion = libTorch.apiVersion;
String flavor = libTorch.flavor;

    // always use cache dir, cache dir might be different from libTorch.dir
    Path cacheDir = Utils.getEngineCacheDir("pytorch");
    Path dir = cacheDir.resolve(version + '-' + flavor + '-' + classifier);
    Path path = dir.resolve(djlVersion + '-' + JNI_LIB_NAME);
    logger.info("lib path {} ", path);// to be added
    if (Files.exists(path)) {
        return path;
    }