Run r66972 assertion only when a sticky-bit makes sense

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@66973 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

test/fileutils/test_fileutils.rb

@@ -742,13 +742,14 @@ class TestFileUtils < Test::Unit::TestCase
     assert_file_not_exist 'tmp/tmpdir/c'
 
     File.chmod(01777, 'tmp/tmpdir')
-    Dir.mkdir 'tmp/tmpdir/d', 0
-    assert_raise(Errno::EACCES) {remove_entry_secure 'tmp/tmpdir/d'}
-    File.chmod 0777, 'tmp/tmpdir/d'
-    Dir.rmdir 'tmp/tmpdir/d'
+    if File.sticky?('tmp/tmpdir')
+      Dir.mkdir 'tmp/tmpdir/d', 0
+      assert_raise(Errno::EACCES) {remove_entry_secure 'tmp/tmpdir/d'}
+      File.chmod 0777, 'tmp/tmpdir/d'
+      Dir.rmdir 'tmp/tmpdir/d'
+    end
 
     Dir.rmdir 'tmp/tmpdir'
-
   end
 
   def test_remove_entry_secure_symlink