Create a dummy minitest.gemspec for a bundled gem

To use the repository version of bundled gems, we need to build a gem by
"gem build", but the repository of minitest does not include
minitest.gemspec because it uses hoe.

This change creats a dummy minitest.gemspec to pass the CI.

tool/lib/bundled_gem.rb

@@ -18,6 +18,31 @@ module BundledGem
     outdir = File.expand_path(outdir)
     gemdir, gemfile = File.split(gemspec)
     Dir.chdir(gemdir) do
+      if gemspec == "gems/src/minitest/minitest.gemspec" && !File.exist?("minitest.gemspec")
+        # The repository of minitest does not include minitest.gemspec because it uses hoe.
+        # This creates a dummy gemspec.
+        File.write("minitest.gemspec", <<END)
+Gem::Specification.new do |s|
+  s.name = "minitest"
+  s.version = #{ File.read("lib/minitest.rb")[/VERSION = "(.+?)"/, 1].dump }
+
+  s.require_paths = ["lib"]
+  s.authors = ["Ryan Davis"]
+  s.date = "#{ Time.now.strftime("%Y-%m-%d") }"
+  s.description = "(dummy gemspec)"
+  s.email = ["ryand-ruby@zenspider.com"]
+  s.extra_rdoc_files = ["History.rdoc", "Manifest.txt", "README.rdoc"]
+  s.files = [#{ Dir.glob("**/*").reject {|s| File.directory?(s) }.map {|s| s.dump }.join(",") }]
+  s.homepage = "https://github.com/seattlerb/minitest"
+  s.licenses = ["MIT"]
+  s.rdoc_options = ["--main", "README.rdoc"]
+  s.summary = "(dummy gemspec)"
+
+  s.add_development_dependency(%q<rdoc>, [">= 4.0", "< 7"])
+  s.add_development_dependency(%q<hoe>, ["~> 4.0"])
+end
+END
+      end
       spec = Gem::Specification.load(gemfile)
       abort "Failed to load #{gemspec}" unless spec
       abort "Unexpected version #{spec.version}" unless spec.version == Gem::Version.new(version)