Revert "portbuild: Pass -j for parallel builds to cargo"
Revert "portbuild: Pass -j for parallel builds to cargo"

The -jX argument is only valid after the sub-command, for example
'cargo build -j4', but 'cargo -j4' is invalid. We do not know the way
the build.* options are set up in the Portfile, therefore this method
is not reliable.

This reverts commit d1271bcdd33efd3a64d62cdc9aa35acc9a06cad0.

macports/macports-base,danchr/macports-base,neverpanic/macports-base,macports/macports-base,neverpanic/macports-base,danchr/macports-base