Build mam.node.js library

[jeremyHD]

Hi, I try to build mam.node.js with yarn. After many environment setups I finally successfully build it.
But I got this message when I try to run scripts in example folder

TypeError: IOTA.cwrap is not a function
    at Object.Module (/Users/jeremyyang/Developer/iota/mam.client.js/lib/mam.node.js:9300:31)
    at __webpack_require__ (/Users/jeremyyang/Developer/iota/mam.client.js/lib/mam.node.js:30:30)
    at /Users/jeremyyang/Developer/iota/mam.client.js/lib/mam.node.js:73:18
    at /Users/jeremyyang/Developer/iota/mam.client.js/lib/mam.node.js:76:10
    at webpackUniversalModuleDefinition (/Users/jeremyyang/Developer/iota/mam.client.js/lib/mam.node.js:3:20)
    at Object.<anonymous> (/Users/jeremyyang/Developer/iota/mam.client.js/lib/mam.node.js:10:3)
    at Module._compile (module.js:643:30)
    at Object.Module._extensions..js (module.js:654:10)
    at Module.load (module.js:556:32)
    at tryModuleLoad (module.js:499:12)

But the compiled mam.node.js on the repo runs successfully on my computer.