Add addr2line back to cross tools

[emaste]

Summary

Also add a comment explaining why it's here.

[emaste]

Makefile.inc1

1440–1441 ↗

(On Diff #3305)

Let me know if you have suggestions for a better comment - e.g., a brief reference to the way you set up a build sandbox.

[imp]

Maybe something akin to:

While no longer required for the build, cross architecture versions of these tools
have proven useful to have around, and were provided in prior versions of FreeBSD.
There's no convenient way to get this functionality otherwise, and the extra cost
of providing it here is offset by its usefulness

But even that's a bit too long...

[• ian]

If I could describe my build sandboxes setup with even a modicum of brevity I would do a wiki page on it (people keep asking me to). I think the comment you wrote is plenty good enough, thanks.

[emaste]

Closed by commit rS277612 (authored by @emaste).