Standalone bundle's setup.rb should implement Gem.try_activate to avoid breaking binding.irb

Describe the problem as clearly as you can

I set --disable-gems in my RUBYOPT variable.

binding.irb causes a call to Gem.try_activate whenever the Gem constant is defined.

Standalone bundles include a bundler/setup.rb file, which defines the Gem constant even when Rubygems isn't required.

Thus, for me, binding.irb doesn't work with standalone bundles.

Did you try upgrading rubygems & bundler?

No, because I can see that Bundler's implementation is still incorrect: https://github.com/rubygems/rubygems/blob/master/bundler/lib/bundler/installer/standalone.rb#L79-L97

Post steps to reproduce the problem

• export RUBYOPT=--disable-gems
• Install a standalone bundle
• After requiring bundler/setup from the standalone bundle, add a binding.irb statement
• Observe the undefined method error on Gem.try_activate

Which command did you run?

bundle install --standalone

What were you expecting to happen?

binding.irb to work

What actually happened?

binding.irb didn't work

If not included with the output of your command, run bundle env and paste the output below

Not sure how to do this

Start in bundler/lib/bundler/installer/standalone.rb at the linked implementation and inspect how the standalone bundle's setup.rb defines Gem. Reproduce with RUBYOPT=--disable-gems, bundle install --standalone, and binding.irb; done means binding.irb works after requiring the standalone setup file without an undefined Gem.try_activate error.