update CONTRIBUTING.md

CONTRIBUTING.md

@@ -26,6 +26,10 @@ Please refer to [README.MD at tutorials/katacoda](tutorials/katacoda/README.md#c
 
 Recommend to use [`as-package.sh`](as-package.sh) to package, which will auto-install the latest Arthas to local `~/.arthas` and when debugging, Arthas will auto-load the latest version.
 
+* To support jni, cpp compiling environment support is required
+* mac needs to install xcode
+* windows need to install gcc
+
 F.Y.I
 1. when using [`as.sh`](https://github.com/alibaba/arthas/blob/master/bin/as.sh) to start Arthas, it will get the latest version under `~/.arthas/lib`;
 2. when [`as-package.sh`](as-package.sh) packaging, it will get the version from `pom.xml` and suffix it with the current timestamp e.g. `3.0.5.20180917161808`. 
@@ -91,6 +95,11 @@ Tip: you can use `--versions` to list all available versions.
 
 本地开发时，推荐执行`as-package.sh`来打包，会自动安装最新版本的arthas到`~/.arthas`目录里。debug时会自动使用最新版本。
 
+* 代码里要编译jni，需要cpp编译环境支持
+* mac需要安装xcode
+* windows需要安装gcc
+
+
 `as.sh`在启动时，会对`~/.arthas/lib`下面的目录排序，取最新的版本。`as-package.sh`在打包时，会取`pom.xml`里的版本号，再拼接上当前时间，比如： `3.0.5.20180917161808`，这样子排序时取的就是最新的版本。
 
 也可以直接 `./mvnw clean package -DskipTests`打包，生成的zip在 `packaging/target/` 下面。但是注意`as.sh`启动加载的是`~/.arthas/lib`下面的版本。