On ruby 1.8.7 a Tempfile can be unlinked only once

Author: drbrain

lib/rubygems/ext/ext_conf_builder.rb

@@ -57,7 +57,7 @@ def self.build(extension, directory, dest_path, results, args=[])
         ENV["DESTDIR"] = destdir
       end
     end
-    t.unlink if t
+    t.unlink if t and t.path
   ensure
     FileUtils.rm_rf tmp_dest if tmp_dest
   end