Add patching for Bundler standalone setup.rb for RubyGems API compatibility

Author: ledsun

lib/ruby_wasm/packager/core.rb

@@ -221,9 +221,27 @@ def _build_gem_exts(executor, build, gem_home)
       ]
 
       executor.system(*args, env: env)
+      patch_bundler_standalone_setup(local_path)
       executor.cp_r(local_path, gem_home)
     end
 
+    # Bundler standalone may generate setup.rb that unconditionally calls
+    # Gem.ruby_api_version. Ruby head can temporarily miss this API while still
+    # exposing Gem.extension_api_version, so we rewrite the generated setup file
+    # to use a fallback expression and keep packaged runtimes loadable.
+    def patch_bundler_standalone_setup(local_path)
+      setup_rb = File.join(local_path, "bundler", "setup.rb")
+      return unless File.file?(setup_rb)
+
+      content = File.read(setup_rb)
+      fallback = "Gem.respond_to?(:ruby_api_version) ? Gem.ruby_api_version : Gem.extension_api_version"
+      patched = content.gsub("Gem.ruby_api_version", fallback)
+      return if patched == content
+
+      RubyWasm.logger.info("Patching #{setup_rb} for RubyGems API compatibility")
+      File.write(setup_rb, patched)
+    end
+
     def cache_key(digest)
       derive_build.cache_key(digest)
     end