...after 84b36c70 "Drop support for MSVC 2013".

Make this a fatal configuration error for now.  The check should be removed
completely after LO 5.4 branch-off.

Change-Id: If2f196abb93607dde9ba5c4f04d219679585e633
Reviewed-on: https://gerrit.libreoffice.org/34822Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>