[rubygems/rubygems] Make --standalone play nice with --local

I'm not sure if using relative paths in the generated script is best for
this case, since it makes the script not movable, but that can be
improved later.

https://github.com/rubygems/rubygems/commit/7f5bdbb842

lib/bundler/cli/install.rb

@@ -148,7 +148,7 @@ module Bundler
       Bundler.settings.set_command_option :path, nil if options[:system]
       Bundler.settings.set_command_option_if_given :path, options[:path]
 
-      if options["standalone"] && Bundler.settings[:path].nil?
+      if options["standalone"] && Bundler.settings[:path].nil? && !options["local"]
         Bundler.settings.temporary(:path_relative_to_cwd => false) do
           Bundler.settings.set_command_option :path, "bundle"
         end

lib/bundler/installer/standalone.rb

@@ -47,7 +47,7 @@ module Bundler
     end
 
     def bundler_path
-      Bundler.root.join(Bundler.settings[:path], "bundler")
+      Bundler.root.join(Bundler.settings[:path].to_s, "bundler")
     end
 
     def gem_path(path, spec)

spec/bundler/install/gems/standalone_spec.rb

@@ -461,3 +461,31 @@ RSpec.describe "bundle install --standalone run in a subdirectory" do
 
   include_examples("bundle install --standalone")
 end
+
+RSpec.describe "bundle install --standalone --local" do
+  before do
+    gemfile <<-G
+      source "#{file_uri_for(gem_repo1)}"
+      gem "rack"
+    G
+
+    system_gems "rack-1.0.0", :path => default_bundle_path
+  end
+
+  it "generates script pointing to system gems" do
+    bundle "install --standalone --local --verbose"
+
+    expect(out).to include("Using rack 1.0.0")
+
+    load_error_ruby <<-RUBY, "spec"
+      require "./bundler/setup"
+
+      require "rack"
+      puts RACK
+      require "spec"
+    RUBY
+
+    expect(out).to eq("1.0.0")
+    expect(err).to eq("ZOMG LOAD ERROR")
+  end
+end