Building compat90 on netbsd-9

[David Brownlee <abs%absd.org@localhost>]

Hi

The changes for PR#56597 stopped compat90 from being built on netbsd-9
(they also stopped building and installing compat90 on netbsd-9 from
completely breaking the system, so it's not like they were a bad move)

I believe the other changes now make compat90 safe to install and
uninstall on netbsd-9 (but obviously still not at all useful there).

However it is very useful to anyone installing -current and wanting to
use netbsd-9 binary packages.

Currently to do this they have to download pkgsrc, just to build and
install compat90 (plus cwrappers and friends), only then can use
binary packages.

This feels like an experience which could be improved :)

Would it be feasible to allow compatXX package to build but not
install on the matching netbsd version, or maybe a flag to override to
allow building for bulk builds?

Thanks

David