v1.0.0 attempts to require_relative non-existent path

[owst]

Problem

Attempting to require 'rackup' with v1.0.0 fails with:

`require_relative': cannot load such file -- /Users/owenstephens/.rbenv/versions/3.1.3/lib/ruby/gems/3.1.0/gems/rackup-1.0.0/lib/rackup/handler

Reproduction

An example Gemfile:

source "https://rubygems.org"

gem "rails", '7.1.2'
gem "redis-rack", "2.1.4" # Depends on Rack < 3

after bundle installing, attemping bundle exec ruby -rrackup -e 'p 42' errors as above.

Background

We're midway through upgrading our app to Rails 7.1; we now depend on Rails 7.1, but do not yet depend on Rack 3, due to a third-party dependency that doesn't support Rack >= 3. We also use Tapioca to generate RBI files. As part of the RBI generation process, the app dependencies are required, including rackup.