The prefix should apply both inside and outside the system. Having the
full host path there only confuses software that is built inside the
system, as well as other ports that prepend the host path themselves
additionally.
All of these patches did the same thing, which is already in upstream
config.sub.
With this change, we need only add `use_fresh_config_sub=true` to
the package.sh file.
Note that this is not done automatically in case the port has a modified
config.sub file.
We may need entries with spaces in makeopts, installopts, and
configopts, and at that point we should also convert depends and
auth_opts to avoid confusion.
