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

Begin with the reported project-www/build and www/build contents and the listed Ionic CLI, app-scripts, Node, and npm versions. Reproduce the missing vendor.js, main.js, and main.css errors on Windows 10, then trace the CLI build path to determine why those assets are not produced. Done means the build creates the expected assets and the reported 404s no longer occur.

Rédigé par le modèle d'indexation à partir du texte de l'issue.