I don′t know if it′s a bug or just not documented, but it seems that you need to add a output path for watching with ng build -o dist -w
while dist is your output path.
Update:
The command is now: ng build -op dist -w
Update 2:
The command is now: ng build --output-path dist --watch
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…