Mark this port BROKEN on powerpc64 the same as on the other archs.
While here, pet portlint by combining BROKEN_arch statements.
The exact error message varies by version, e.g.:
checking build system type... Invalid configuration 'powerpc64-portbld-freebsd12.1': machine `powerpc64-portbld' not recognized checking build system type... Invalid configuration 'powerpc64-portbld-freebsd13.0': machine `powerpc64-portbld' not recognized
Approved by: portmgr (tier-2 blanket)