Cherry-picked spec/mspec/lib/mspec/helpers/fs.rb

From 316f60e3be

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@66147 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

spec/mspec/lib/mspec/helpers/fs.rb

@@ -1,12 +1,6 @@
 # Copies a file
 def cp(source, dest)
-  File.open(dest, "wb") do |d|
-    File.open(source, "rb") do |s|
-      while data = s.read(1024)
-        d.write data
-      end
-    end
-  end
+  IO.copy_stream source, dest
 end
 
 # Creates each directory in path that does not exist.