diff -r 39b9b05c3085 Lib/distutils/sysconfig.py

--- a/Lib/distutils/sysconfig.py	Wed Apr 10 00:27:23 2013 +0200

+++ b/Lib/distutils/sysconfig.py	Wed Apr 10 10:14:18 2013 +0200

@@ -362,7 +362,10 @@

                     done[n] = item = ""

                 if found:

                     after = value[m.end():]

-                    value = value[:m.start()] + item + after

+                    value = value[:m.start()]

+                    if item.strip() not in value:

+                        value += item

+                    value += after

                     if "$" in after:

                         notdone[name] = value

                     else:

diff -r 39b9b05c3085 Lib/sysconfig.py

--- a/Lib/sysconfig.py	Wed Apr 10 00:27:23 2013 +0200

+++ b/Lib/sysconfig.py	Wed Apr 10 10:14:18 2013 +0200

@@ -296,7 +296,10 @@

                 if found:

                     after = value[m.end():]

-                    value = value[:m.start()] + item + after

+                    value = value[:m.start()]

+                    if item.strip() not in value:

+                        value += item

+                    value += after

                     if "$" in after:

                         notdone[name] = value

                     else: