Disable LTO for now - suspected cause of fdo#73464.

Change-Id: I8c9ff1342ecb6b7a990ea643c505e9dedf5de659
Reviewed-on: https://gerrit.libreoffice.org/7682
Reviewed-by: Markus Mohrhard <markus.mohrhard@googlemail.com>
Reviewed-by: Michael Stahl <mstahl@redhat.com>
Reviewed-by: Christian Lohmaier <lohmaier+LibreOffice@googlemail.com>
Tested-by: Christian Lohmaier <lohmaier+LibreOffice@googlemail.com>