no pages built in project-www/build is almost empty

**Description:**
I am trying to run my project but it seems that files are never built www/build directory contains only 2 files : polyfilles.js and sw-toolbox.js

**Output:**
Failed to load resource: the server responded with a status of 404 (Not Found)
vendor.js Failed to load resource: the server responded with a status of 404 (Not Found)
main.js Failed to load resource: the server responded with a status of 404 (Not Found)

:8100/build/main.css Failed to load resource: the server responded with a status of 404 (Not Found)
vendor.js Failed to load resource: the server responded with a status of 404 (Not Found)
main.js Failed to load resource: the server responded with a status of 404 (Not Found)
main.css Failed to load resource: the server responded with a status of 404 (Not Found)
ion-dev.js?v=3.1.7-201801172029:120 Dev server logger closed
13livereload.js?snipver=1:76 WebSocket connection to 'ws://localhost:35729/livereload' failed: Error in connection establishment: net::ERR_CONNECTION_REFUSED

**My `ionic info`:**
cli packages: (C:\Users\User\AppData\Roaming\npm\node_modules)

@ionic/cli-utils : 1.19.1
ionic (Ionic CLI) : 3.19.1

global packages:

cordova (Cordova CLI) : 8.0.0

local packages:

@ionic/app-scripts : 3.1.7-201801172029
Cordova Platforms : android 6.2.3 ios 4.4.0
Ionic Framework : ionic-angular 3.9.2

System:

Node : v8.9.1
npm : 5.6.0
OS : Windows 10

Environment Variables:

ANDROID_HOME : not set

Misc:

backend : pro

從報告的 project-www/build 和 www/build 內容以及列出的 Ionic CLI、app-scripts、Node 和 npm 版本開始。在 Windows 10 上重現缺少 vendor.js、main.js 和 main.css 的錯誤，然後追蹤 CLI 建置路徑，以確定為什麼沒有產生這些資源。當建置產生預期的資源且報告的 404 不再發生時，即表示完成。

由索引模型根據 Issue 內容生成。