Add missing space to fix r73681 changes.

We need a space between the command and stderr redirection to avoid the "2"
from being taken as part of the last option on the command line.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@73687 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775