Allow additional "options" files to be specified in kernel config

[stevek]

Summary

The "includeoptions" directive can be used to specify an additional
options file to be used.

This is useful in conjunction with the "files" directive for build
environments to be able to add custom files and options.

Obtained from: Juniper Networks, Inc.

[imp]

Generally, it's fine, but I have a question...

usr.sbin/config/mkoptions.cc

372

this is unusual... why is it needed?

[stevek]

usr.sbin/config/mkoptions.cc

372

I missed that from when I was debugging some issues. Although it might be good to add a "verbose" flag and put prints such as this under a if (verbose) type of conditional.

I know it was useful when I was adding things for Juniper build where we have Juniper-specific changes under a top-level juniper/ directory and the "includeoptions" entry looks like this:
includeoptions "../../../juniper/sys/conf/options"

If one sets an includeoptions and the path is wrongly specified, it's useful to be able to have a message indicating what was trying to be read and the cwd that is the root of a relative path.

What do you think about adding a verbose flag and putting this under such a conditional (and possibly adding additional prints in other places under said conditional)?

[imp]

usr.sbin/config/mkoptions.cc

372

A verbose flag would be fine...

[stevek]

Added -v flag for verbose mode. Added man page details for the flag.