Subcommand feature does not work on Ubuntu

[norio-nomura]

Since /usr/bin/which rejects -s argument.
Reproducing steps on Ubuntu with SwiftLint:

$ docker run -it --rm norionomura/swiftlint:swift-4.2 bash
root@5d3cc0804b2c:/# echo "echo swiftlint-test executed">/usr/bin/swiftlint-test
root@5d3cc0804b2c:/# chmod +x /usr/bin/swiftlint-test
root@5d3cc0804b2c:/# swiftlint test
Illegal option -s
Usage: /usr/bin/which [-a] args
Unrecognized command: 'test'. See `swiftlint help`.