fileutils.rb: fix rename_cannot_overwrite_file

* lib/fileutils.rb (rename_cannot_overwrite_file): File.rename on
  cygwin and mswin/mingw can overwrite the destination file.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@51696 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

lib/fileutils.rb

@@ -547,7 +547,7 @@ module FileUtils
   OPT_TABLE['move'] = [:force, :noop, :verbose, :secure]
 
   def rename_cannot_overwrite_file?   #:nodoc:
-    /cygwin|mswin|mingw|bccwin|emx/ =~ RUBY_PLATFORM
+    /emx/ =~ RUBY_PLATFORM
   end
   private_module_function :rename_cannot_overwrite_file?