cmake hangs on kqueue

[Manuel Bouyer <bouyer%antioche.eu.org@localhost>]

Hello,
on a box building packages, running with a -current amd64 kernel and
9.0_STABLE userland, I see pbulk build hanging.
All related processes are in wait state, exept cmake which is in kqueue,
and this is reproductible (if I kill this cmake instance, pbulk will
proceeed with the next package until it hangs on another cmake instance)
 100  9698 22944 57478  78  0 127384   8620 kqueue  Il+  pts/0   0:00.04 /usr/pkg/bin/cmake -E cmake_autogen /work/graphics/gwenview/work/gwenview-20.04.1/_KDE_build/tests/auto/CMakeFiles/imagescalertest_autogen.dir/AutogenInfo.json

kernel is
9.99.77 build on Sun Jan 10 08:56:13 UTC 2021 (I guess from up to date
sources, but I didn't build it myself and I don't have access to the sources).
Userland is
NetBSD 9.0_STABLE/amd64
      Build date   Thu Jun 11 22:49:34 UTC 2020

I think I've seen some mails about a similar problem in the past few months
but I don't remember the details (and couldn't find a PR about it either).

Does it ring a bell to someone ?

-- 
Manuel Bouyer <bouyer%antioche.eu.org@localhost>
     NetBSD: 26 ans d'experience feront toujours la difference
--