Use original Bundler binstub from RubyGems to avoid version argument issues

[vinistock]

Motivation

Closes #2862 and #2731 (comment)

Clearly, adding the Bundler version to the command causes trouble for people using binstubs in certain configurations.

I think I found a way to continue specifying the version, which guarantees that RubyGems will eagerly activate the right specification, while at the same time avoiding those issues.

Implementation

The idea is to invoke the original Bundler binstub generated by RubyGems directly. That way, even if there's a custom binstub, we avoid invoking it and use the default one (which accepts the version).

Automated Tests

Managed to write a test that fails before this fix.

Manual tests

1. Create an executable file bin/bundle
2. Add this code to the executable

#!/usr/bin/env ruby
raise "This should not be called"

3. Add the bin directory to your PATH temporary: export PATH ./bin:$PATH
4. Verify that booting the LSP does not fail exe/ruby-lsp

[vinistock]

• Use original Bundler binstub from RubyGems to avoid version argument issues #2987 👈 (View in Graphite)
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