editors/openoffice-{4,devel}: parallel build fail

The Apache OpenOffice ports frequently fail to build with errors similar
to:

nm: '../unxfbsdi.pro/slo/b2dcubicbezier.o': Invalid argument

but only parallel builds on 13.X and 14.X. I've never seen this on
15.0-CURRRENT. The root cause is not yet known.

Disable parallel builds for FreebSD < 15.0.

Reported by: pkg-fallout
MFH: 2025Q3

(cherry picked from commit f733d1749456aa27393d0455a96b5eb18044a75d)