어이없게도 해결법은 os를 업그레이드(to Catalina 10.15.1)하는 것이었다.
ref: https://forums.developer.apple.com/thread/125322
Xcode 11.2 not updating. |Apple Developer Forums
I have a same problem when updating to xcode 11.2. At first, the message of launchpad's status told me "Downloading x.xx of 4.16 GB". After done downloading, the message showed me "Installing", but after for a while, the download process started again auto
forums.developer.apple.com
happy hackin'
