Apply fix from r85784 on py3k too.

Fixes bug #10126 for Python 3.2 by using $RUNSHARED to find the
directory to the shared library.  test_distutils now passes when
Python was built with --enable-shared (Barry didn’t have the error
but I did).

tests/test_build_ext.py

@@ -52,8 +52,12 @@ class BuildExtTestCase(TempdirManager,
         # Extension() instance because that doesn't get plumbed through to the
         # final compiler command.
         if not sys.platform.startswith('win'):
-            library_dir = sysconfig.get_config_var('srcdir')
-            cmd.library_dirs = [('.' if library_dir is None else library_dir)]
+            runshared = sysconfig.get_config_var('RUNSHARED')
+            if runshared is None:
+                cmd.library_dirs = ['.']
+            else:
+                name, equals, value = runshared.partition('=')
+                cmd.library_dirs = value.split(os.pathsep)
 
     def test_build_ext(self):
         global ALREADY_TESTED