Run bffvalidator also from Linux, reportedly works from wine 1.9
upwards. Wraps stuff in a shell for path name conversion.

Change-Id: I3093b10bbbf89aaff97f63485b8ccadb417b3561
Reviewed-on: https://gerrit.libreoffice.org/26784Reviewed-by: Thorsten Behrens <Thorsten.Behrens@CIB.de>
Tested-by: Thorsten Behrens <Thorsten.Behrens@CIB.de>