新增于: v0.1.100
process.execPath 属性返回启动 Node.js 进程的可执行文件的绝对路径名。
符号链接（如果有）会被解析。
'/usr/local/bin/node'
Added in: v0.1.100
The process.execPath property returns the absolute pathname of the executable
that started the Node.js process. Symbolic links, if any, are resolved.
'/usr/local/bin/node'