npm prestart script for triggering sub-app builds

prestart.js

// @see https://strongloop.com/strongblog/modular-node-js-express/

var fs = require('fs')
var resolve = require('path').resolve
var join = require('path').join
var cp = require('child_process')

// get library path
var src = resolve(__dirname, '../src/')

fs.readdirSync(src)
  .forEach((app) => {
        var appPath = join(src, app)

        // ensure path has package.json
        if (!fs.existsSync(join(appPath, 'package.json'))) return

        // install folder
        cp.spawn('npm', ['run', 'build'], {
            env: process.env,
            cwd: appPath,
            stdio: 'inherit'
        })
    })