rbinstall.rb: Gem::Installer lacks dir_mode option

* tool/rbinstall.rb (bundle-gems): Gem::Installer does not support
  directory permission option, set umask to owner writable.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@57546 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

tool/rbinstall.rb

@@ -845,7 +845,14 @@ def install_default_gem(dir, srcdir)
       inst = Gem::Installer.new(gem, options)
       inst.spec.extension_dir = with_destdir(inst.spec.extension_dir)
       begin
-        Gem::DefaultUserInteraction.use_ui(silent) {inst.install}
+        Gem::DefaultUserInteraction.use_ui(silent) do
+          begin
+            File.umask(022)
+            inst.install
+          ensure
+            File.umask(0222)
+          end
+        end
       rescue Gem::InstallError => e
         next
       end