merge revision(s) 57543: [Backport #13194]
rbinstall.rb: default umask * tool/rbinstall.rb: revert r49841 and default umask to just prohibit all from writing. symlink(2) has no argument to set permissions but is affected by umask. [ruby-dev:49975] [Bug #13194]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_3@58152 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
merge revision(s) 57543: [Backport #13194]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_3@58152 b2dd03c8-39d4-4d8f-98ff-823fe69b080e