Denying write permissions to the owner seems wrong.
Oddly, this problem only manifests in the "ruby_2_4" branch when
installing bundled gems (rake and friends). It does not happen
with "ruby_2_3", or "trunk", so it might be related to RubyGems
changes.
* tool/rbinstall.rb: set umask to 022
[ruby-core:84420] [Bug #14227]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@61611 b2dd03c8-39d4-4d8f-98ff-823fe69b080e