### Please describe the problem.

Utility/libkqueue.h is missing from git-annex-8.20210127.tar.gz as hosted on hackage.

```
SHA256 (/usr/ports/distfiles/hackage/git-annex-8.20210127.tar.gz) = 636f439420f28a92a8250b9f8b422567e439315f3f2d23cb0bea3b0a0e5755c3
% tar ztf /usr/ports/distfiles/hackage/git-annex-8.20210127.tar.gz | grep libkqu
git-annex-8.20210127/Utility/libkqueue.c
```

### What steps will reproduce the problem?

Building on `(! os(solaris) && ! os(gnu) && ! os(linux))` causes a complaint about this file missing.

### What version of git-annex are you using? On what operating system?

git-annex-8.20210127 on OpenBSD 6.8-current amd64

### Please provide any additional information below.

[[!format sh """
$ doas pkg_add libmagic
$ cabal get git-annex-8.20210127
$ cabal v2-build --extra-include-dirs=/usr/local/include --extra-lib-dirs=/usr/local/lib
...
  checking UPGRADE_LOCATION... not available
  checking git... yes
  checking git version... 2.30.0
  checking cp -a... yes
  checking cp -p... yes
  checking cp --preserve=timestamps... no
  checking cp --reflink=auto... no
  checking xargs -0... yes
  checking rsync... yes
  checking curl... yes
  checking bup... no
  checking nice... yes
  checking ionice... no
  checking nocache... no
  checking gpg... gpg
  checking lsof... not available
  checking git-remote-gcrypt... not available
  checking ssh connection caching... yes
fatal: not a git repository (or any parent up to mount point /)
Stopping at filesystem boundary (GIT_DISCOVERY_ACROSS_FILESYSTEM not set).
Configuring git-annex-8.20210127...
setup: Missing dependency on a foreign library:
* Missing (or bad) header file: Utility/libkqueue.h
...
"""]]

### Have you had any luck using git-annex before?

Nope, but hopefully packaging up the file will make it a little easier for me to try the next time :)


> [[fixed|done]] in git for next release --[[Joey]]
