Added bundler as default gems. Revisit [Feature #12733]

* bin/*, lib/bundler/*, lib/bundler.rb, spec/bundler, man/*:
    Merge from latest stable branch of bundler/bundler repository and
    added workaround patches. I will backport them into upstream.
  * common.mk, defs/gmake.mk: Added `test-bundler` task for test suite
    of bundler.
  * tool/sync_default_gems.rb: Added sync task for bundler.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@65509 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

spec/bundler/install/process_lock_spec.rb

@@ -0,0 +1,35 @@
+# frozen_string_literal: true
+
+RSpec.describe "process lock spec" do
+  describe "when an install operation is already holding a process lock" do
+    before { FileUtils.mkdir_p(default_bundle_path) }
+
+    it "will not run a second concurrent bundle install until the lock is released" do
+      thread = Thread.new do
+        Bundler::ProcessLock.lock(default_bundle_path) do
+          sleep 1 # ignore quality_spec
+          expect(the_bundle).not_to include_gems "rack 1.0"
+        end
+      end
+
+      install_gemfile! <<-G
+        source "file://#{gem_repo1}"
+        gem "rack"
+      G
+
+      thread.join
+      expect(the_bundle).to include_gems "rack 1.0"
+    end
+
+    context "when creating a lock raises Errno::ENOTSUP", :ruby => ">= 1.9" do
+      before { allow(File).to receive(:open).and_raise(Errno::ENOTSUP) }
+
+      it "skips creating the lock file and yields" do
+        processed = false
+        Bundler::ProcessLock.lock(default_bundle_path) { processed = true }
+
+        expect(processed).to eq true
+      end
+    end
+  end
+end