devel/icu: unbreak on big-endian after r496981

gmake[2]: *** No rule to make target 'out', needed by 'out/icudt64b.dat'. Stop.
gmake[2]: Leaving directory '/usr/ports/devel/icu/work/icu/source/data'

PR: 236860
Reported by: Piotr Kubaj, pkg-fallout
Obtained from: Gentoo