Bundler 4 seems to break engine_cart

[jrochkind]

The exact reasons why are unclear to me; possibly more things need to be wrapped in Bundler.with_unbundined_env. (or even a use case for the slightly different with_original_env)?

I don't understand this well enough to fully spec it, please feel free to edit this descirption if you do.

Some background though, what we do know

• blacklight using bundler <4 to work around: Avoid bundler 4 since it causes issues with engine_cart projectblacklight/blacklight#3784
  • a failing BL CI: https://github.com/projectblacklight/blacklight/actions/runs/20079840341/job/57603875568?pr=3783
• @jcoyne opened an issue on rubygems: Bundler 4.0.1 trying to find gem for every platform ruby/rubygems#9176 (comment)
• bl_range_limit notes Lock to bundler < 4 to fix CI projectblacklight/blacklight_range_limit#328
  • a failing bl_range_limit CI: https://github.com/projectblacklight/blacklight_range_limit/actions/runs/20050712705/job/57505810337
• Rails itself having a similar problem: PluginTestRunnerTest gets Could not find gems matching 'thruster' valid for all resolution platforms  rails/rails#56234
  • resulting in this ticket filed by rails on rubygems: Rails CI PluginTestRunnerTest gets Could not find gems matching 'thruster' valid for all resolution platforms  ruby/rubygems#9130
  • Which got closed and resulted in a new ticket back on rails: Ensure PluginTestRunnerTest and TestRunnerInEngineTest use clean Bundler env rails/rails#56247