Install zeitwerk without bundle install

Author: hsbt

common.mk

@@ -1659,6 +1659,8 @@ test-bundler-prepare: $(TEST_RUNNABLE)-test-bundler-prepare
 no-test-bundler-prepare: no-test-bundler-precheck
 yes-test-bundler-prepare: yes-test-bundler-precheck
 	$(ACTIONS_GROUP)
+	$(XRUBY) -C "$(srcdir)" bin/gem install --no-document \
+		--install-dir .bundle --conservative "zeitwerk"
 	$(XRUBY) -C $(srcdir) -Ilib \
 		-e 'ENV["GEM_HOME"] = File.expand_path(".bundle")' \
 		-e 'ENV["BUNDLE_APP_CONFIG"] = File.expand_path(".bundle")' \

tool/bundler/test_gems.rb

@@ -13,6 +13,3 @@
 gem "builder", "~> 3.2"
 gem "rb_sys"
 gem "rubygems-generate_index", "~> 1.1"
-
-# for bundled_gems_spec.rb
-gem "zeitwerk", "~> 2.7"