install fails because / is not writeable

[[LoN]Kamikaze]

Once in a while a port fails to upgrade, because it wants to write something in /etc. E.g. perl into /etc/make.conf or other ports into /etc/group.

On my systems / is normally a read only mount. These ports build fine during a portupgrade and fail during install, leaving most of the port installed, but unregistered (i.e. the package database is broken).

I think such ports should set something like USE_WRITE_SLASH=yes and refuse to install if / is not writeable.