`skip doctor` fails for lack of `xcodebuild` on fresh install

[dfabulich]

On a fresh machine (e.g. UTM), the initial skip checkup will fail, because installing Homebrew will xcode-select --switch /Library/Developer/CommandLineTools.

[✗] Xcode version: error executing xcodebuild (install from: https://developer.apple.com/xcode/)

In verbose mode:

executing command: /usr/bin/xcodebuild -version
xcode-select: error: tool 'xcodebuild' requires Xcode, but active developer directory '/Library/Developer/CommandLineTools' is a command line tools instance
[✗] Xcode version: error executing xcodebuild (install from: https://developer.apple.com/xcode/)

(It doesn't matter whether you install Homebrew before or after Xcode. Once Homebrew selects the CLT directory, nothing automatically attempts to reset it to Xcode.)