On Ubuntu, the Homebrew cask doesn't install Swift

[dfabulich]

On a fresh Ubuntu, install Homebrew, brew install skiptools/skip/skip and run skip doctor.

$ skip doctor --verbose
Skip Doctor
executing command: /home/linuxbrew/.linuxbrew/bin/skip version
Skip version 1.7.4
[✓] Skip version 1.7.4 (= 1.7.4)
[✗] An executable tool named 'swift' could not be found in the PATH, nor was it specified as part of the command-line flags.
[✗] Skip 1.7.4 doctor failed with 1 error
See https://skip.dev/docs/faq and https://forums.skip.dev for help
See output log for error details: /tmp/skip-doctor-2026-03-07T18:37:58Z.txt
Error: 2 errors