Bug#929720: hkl: FTBFS: ../../hkl/ccan/generator/generator.h:23:2: error: #error Generators require coroutines

[Santiago Vila]

Greetings.

I can reproduce this bug, and I've put a bunch of failed build logs here:

https://people.debian.org/~sanvila/build-logs/hkl/

The bug happens "randomly", but in a very particular way: always in some
instances and never in the others.

I believe this may be some sort of Makefile bug which is related to
filesystem ordering or something similar, but I don't really know.

In either case, I could easily offer ssh access to a machine where
this happens to anybody interested in debugging the problem (please
contact me privately for details).

While we are at it: I'm still doing QA for buster, so I'd appreciate
(once we find a fix) if we could fix this in buster as well (it's a
FTBFS bug after all). I would be willing to help if required, either
by preparing an upload for stable, filing a release.debian.org bug, or
both.

Thanks.