test_fileutils.rb: fix for Mac OS X
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@44399 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
test_fileutils.rb: fix for Mac OS X
OS X, whose getpwnam("") doesn't err. passwd & group databases
format is colon-separated, so user & group name can't contain a
colon.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@44399 b2dd03c8-39d4-4d8f-98ff-823fe69b080e