makeWin32(): Replaced shell syntax specific to cmd.exe Windows flavors

with an alternative that works under command.com too.  Building the
splitters still fails on command.com systems because the synthesized
command lines are very long (command.com appears to truncate them,
leaving gibberish commands).

utilities/ExtensionBuilder.py

@@ -264,7 +264,8 @@ class ExtensionBuilder:
                     module, config
                     ))
 
-                self.doCommand('del *.def *.mak')
+                self.doCommand('del *.def')
+                self.doCommand('del *.mak')
 
                 os.chdir(current_dir)