Eli Zaretskii <eliz@gnu.org> writes:
> More generally, someone who has access to FreeBSD and understands its
> ACL implementation should look into that, because it sounds like we
> have fundamental problems there with moving files from temp directory,
> and those problems are just waiting to bite us in random places, like
> this one.

After a big of digging, I discovered the immediate problem and it does
not have anything to do with FreeBSD's ACL implementations [1].
FreeBSD's package building tool, poudriere has an option to use tmpfs
for some of the file systems including the working directories, however
I do not believe tmpfs supports ACLs.  When I turn this option off, so
that tmpfs is not used, the build finishes successfully without any
patching.

Should ACL support be required to _build_ Emacs, even if that build will
itself support ACLs?

[1] UFS has both POSIX and NFSv4 ACLs, while ZFS only supports NFSv4 ACLs.
    https://www.freebsd.org/doc/handbook/fs-acl.html
    https://wiki.freebsd.org/NFSv4_ACLs
    https://www.freebsd.org/cgi/man.cgi?query=setfacl