osgEarth 加载MapBox的pbf瓦片数据
引接pbf瓦片需要protobuf的库，在cmake时注意添加该库的路径
osgEarth3.7已经封装好了MapBox的专用图层：如下实例：
osgEarth::MapBoxGLImageLayer::Options options;
MapBoxGLImageLayer* mapBoxLayer = new MapBoxGLImageLayer(options);
mapBoxLayer->setURL("https://www.arcgis.com/sharing/rest/content/items/cabd61a6cfc44843b2ccd6969bb88cf0/resources/styles/root.json");
mapBoxLayer->setPixelScale(2.0);
mapBoxLayer->setTileSize(512);
//mapBoxLayer->setProfile(Profile::create(Profile::GLOBAL_GEODETIC));
//mapBoxLayer->setProfile(Profile::create(Profile::GLOBAL_GEODETIC));
map->addLayer(mapBoxLayer);