Fix [1055540 ] bdist_wininst broken for pure Python distributions

Lib/distutils/command/bdist_wininst.py

@@ -116,6 +116,7 @@ class bdist_wininst (Command):
         install_lib.compile = 0
         install_lib.optimize = 0
 
+        if self.distribution.has_ext_modules():
             # If we are building an installer for a Python version other
             # than the one we are currently running, then we need to ensure
             # our build_lib reflects the other Python version rather than ours.