setuptools seems to call os.path.realpath on the paths of working set items.

On Mac OS X the path returned by tempfile.mkdtemp is not the real path.
This makes the realtive_path test of easy_install.txt failing.
Calling os.path.realpath on the base directory fixed this testfailure for python 2.4 - 2.6.

src/zc/buildout/testing.py

@@ -212,6 +212,7 @@ def buildoutSetUp(test):
 
 
     base = tempfile.mkdtemp('buildoutSetUp')
+    base = os.path.realpath(base)
     register_teardown(lambda base=base: rmtree(base))
 
     old_home = os.environ.get('HOME')