Makefile.inc1 copies locales to ${INSTALLTMP} to avoid issues when
running make installworld on a live system. However, this can break
on non-FreeBSD systems, e.g. on openSUSE where /usr/share/locales
has mode 0555, which means after we copy it, we can't delete it,
so the build fails.
Since this functionality is only useful when installing over a
live system, disable it when the build host is not FreeBSD.
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