Fix build on !x86 systems by ensuring option AVX cannot be set:
pkg-static: Unable to access file /wrkdirs/usr/ports/net/openmpi/work/stage/usr/local/%%AVX%%mpi/openmpi/lib/openmpi/mca_op_avx.la:No such file or directory pkg-static: Unable to access file /wrkdirs/usr/ports/net/openmpi/work/stage/usr/local/%%AVX%%mpi/openmpi/lib/openmpi/mca_op_avx.so:No such file or directory
While here, sort the _DESC entries, and gather the OPTIONS_DEFAULT,
OPTIONS_EXCLUDE_*, and OPTIONS_SUB entries together.
Approved by: portmgr (tier-2 blanket)