Otherwise on Windows we can't regenerate reference files.

Change-Id: Ia293fb62651ff981b127893e26ef1d19172d2a2b
Reviewed-on: https://gerrit.libreoffice.org/30788Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Tamás Zolnai <tamas.zolnai@collabora.com>