Index: setup.py
===================================================================
--- setup.py	(revision 83123)
+++ setup.py	(working copy)
@@ -2041,4 +2041,13 @@
 
 # --install-platlib
 if __name__ == '__main__':
+    import os
+
+    # the makefile adds a number of variables to the environment that mirror
+    # the defition in the Makefile. Distutils will append the values from the
+    # environment to the ones in the Makefile, and that can confuse compilers
+    # that don't like duplicate command-line arguments.
+    for name in ('CC', 'LDFLAGS', 'OPT'):
+        if name in os.environ:
+            del os.environ[name]
     main()