Newer version to fix buildout bug.

From changelog:

Make buildout.rmtree working with symlink as a path argument.
  https://bugs.launchpad.net/zc.buildout/+bug/144228

stack/erp5.cfg

@@ -423,7 +423,7 @@ scripts =
 
 [versions]
 # Use SlapOS patched zc.buildout
-zc.buildout = 1.6.0-dev-SlapOS-003
+zc.buildout = 1.6.0-dev-SlapOS-004
 
 # pin Acquisition and Products.DCWorkflow to Nexedi flavour of eggs
 Acquisition = 2.13.7nxd001