Can't update Developer Tools on Mojave
I faced the same problem. The way I have solve the issue is given below.
- I got the new xcode 10.1 from App Store. Though the problem existed.
- Then I run
xcode-select --installwhich didn’t work. - I update my homebrew by
brew update. Than I runsudo xcode-select --reset.
Now it works fine.
I'm the original poster. In the end I resolved the problem by installing the tools manually, with the installer I downloaded from https://developer.apple.com/download/more/.