macOS has this; is there an issue with using FreeBSD's instead? Also how does this actually link? AFAICT libegacy won't have readpassphrase.c?

libbsd provides readpassphrase, which is presumably intended to be compatible, but using -I/usr/include/bsd opens a whole new can of worms.
So this is the simplest solution.

As for mac I expect it should "just work" but not sure if I can test.

Oh... it shouldn't be using libbsd, libegacy is supposed to contain everything needed when cross-building, rather than mixing in-tree things and whatever libbsd's doing.

If I recall correctly I ran into some behaviour differences when using libbsd for the bootstrap tools, so I decided against using it. Since we already have -legacy we can hopefully just add the readpassphrase source to that?

libegacy does not currently provide readpassphrase
so that should be added?
AFAIK that's the only thing missing

That would be fine by me

Yes, we've added things to libegacy as needed for cross-building, it basically functions as a libbsd for cross-building

Just put this in tools/build/includes.h and add that to INCS?

If/when something outside of libegacy needs it
But I could add an includes.h if preferred

Actually -I${.CURDIR} doesn't work we get tools/build/fcntl.h which doesn't work
I put it in cross-build/include/linux

This breaks building the tests for world on !FreeBSD

And whatever the right fix for this is should likely be done elsewhere by whacking MK_TESTS globally?

Ugggg... Please add TESTS to the BROKEN list instead.