libxslt shared library depends on libxml2 library, and for cases when
libxml2 is "external", just-compiled libxslt will have an entry like
/@.__________________________________________________URELIB/lib/libxml2.2.dylib
and the whole LibreOffice application will fail to run

Change-Id: Ifafbdab74151207597ba9bd2e3beb0b8c3aa3ab7
Reviewed-on: https://gerrit.libreoffice.org/20816Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Michael Stahl <mstahl@redhat.com>
Tested-by: Michael Stahl <mstahl@redhat.com>