Re-enable npm run test for renamed head-wasip2 package by fixing Bundler standalone compatibility

[ledsun]

2nd Challenge

Summary

This PR keeps npm run test enabled for the head-wasip2 package flow by explicitly loading RubyGems
before Bundler standalone setup when the runtime is still in a partial Gem state.

Root Cause

This was reproduced locally against the failing Ruby revision:

• 7d4983803887a45c311ab954de4527333b976500

logs: https://github.com/ruby/ruby.wasm/actions/runs/22755141423/job/65997955482#step:16:146

At rubyInit return time in that build, the runtime state was:

• Gem is defined
• Gem.ruby_api_version is missing
• Gem.extension_api_version is missing
• rubygems.rb is not loaded
• $LOAD_PATH does not yet include the main stdlib directories needed for RubyGems
• RbConfig.ruby is still nil

Bundler standalone setup assumes that defined?(Gem) is enough to use RubyGems API helpers. In this runtime state,
that assumption is false, so loading /bundle/bundler/setup.rb fails before tests start.

Fix

Before requiring /bundle/bundler/setup.rb, load RubyGems explicitly when:

• Gem is already defined, and
• Gem.ruby_api_version is still missing

This keeps the workaround scoped to the Bundler standalone path used by the component-model package.

Why This Fix

This issue appears to depend on a specific Ruby revision and ruby.wasm startup state, not on Bundler standalone in
Given that:

• the failure was observed only in a particular runtime state,
• the local reproduction required that exact revision/runtime combination,
• and there is not yet a small standalone upstream reproduction for Bundler,

I think, this fix is better.

1st Challenge

## Summary

This PR re-enables npm run test for the renamed head-wasip2 npm package flow by fixing a Bundler standalone compatibility issue in the packaged ruby- head runtime.

Previously, the check step was effectively not running as intended after the rename. Once re-enabled, it failed during VM boot because generated /bundle/ bundler/setup.rb expected RubyGems API-version helpers that may be missing in this runtime combination.

Goal

Ensure the renamed head-wasip2 package pipeline can run npm run test in CI without being skipped, and pass the boot phase reliably.

Root Cause

bundle install --standalone generates bundle/.../bundler/setup.rb that assumes:

• Gem.ruby_api_version
• Gem.extension_api_version

are available.

In ruby-head packaging/runtime combinations used by this workflow, either method can be missing, causing NoMethodError before tests execute.

What Changed

1) Patch generated Bundler standalone setup after packaging

In RubyWasm::Packager::Core::DynamicLinking#_build_gem_exts, after standalone bundle generation, we now call:

• patch_bundler_standalone_setup(local_path)

This injects a compatibility shim into generated bundler/setup.rb that defines missing RubyGems API-version methods only when absent.

2) Preserve Bundler path semantics

Instead of replacing Gem.*_api_version expressions inline, this PR injects method shims so Bundler’s original extension/load-path logic remains intact
(including shared/static behavior).

This avoids regressions like failing to resolve js.so.

3) Update type signatures

Added RBS declaration for the new private helper method.

Another solution

Modifying bundler install --standalone might be smarter.

[kateinoigakukun]

Makes sense to me! Thanks 🙏
As a follow-up, it might be better to fix Bundler's standalone code generator to detect the missing methods more granularly https://github.com/ruby/rubygems/blob/884d80fd158fead18bb4f021796a2af062a45ac9/bundler/lib/bundler/installer/standalone.rb#L76