Fix infinite recursion in cythonize().

Cython/Build/Dependencies.py

@@ -278,8 +278,8 @@ class DependencyTree(object):
 
     @cached_method
     def package(self, filename):
-        dir = os.path.dirname(filename)
-        if os.path.exists(os.path.join(dir, '__init__.py')):
+        dir = os.path.dirname(os.path.abspath(filename))
+        if dir != filename and os.path.exists(os.path.join(dir, '__init__.py')):
             return self.package(dir) + (os.path.basename(dir),)
         else:
             return ()