--- mkmf.rb	2009-01-27 01:29:14 -0700
+++ mkmf.new.rb	2009-01-27 01:28:40 -0700
@@ -295,6 +295,11 @@
     nil while command.gsub!(varpat) {vars[$1||$2]}
   end
 
+  if /mingw/ =~ CONFIG['build_os'] and
+        /sh/ =~ CONFIG['SHELL']
+   command = "sh -c '#{command}'"
+  end
+
   Logging::open do
     puts command.quote
     system(command)