I believe changeset d4b93e21c2664d6a78e0656e7a7be0807be1c352 may be the cause of buildbot failures on FreeBSD (at least koobs-freebsd-current, log attached), due to only the EBADF error being handled (not EINVAL, et al).

Unfortunately the worker was been offline for a longer than anticipated period of time and only recently was restored which delayed picking it up.

The issue (in this workers case) is related to the buildbot home/data directory being on a ZFS filesystem, who's host was recently updated (from current late last year to yesterday).

Initial investigation/isolation/references:

Disable posix_fallocate(2) for ZFS
https://lists.freebsd.org/pipermail/svn-src-head/2017-November/105709.html

Note: Above change will be relevant (merged) for at least FreeBSD 12 and 11, but perhaps even 10.

0000684: posix_fallocate() should be allowed to return ENOTSUP (Interp Status: Approved)
http://austingroupbugs.net/view.php?id=684

[HEADS UP] posix_fallocate support removed from ZFS, lld affected
https://lists.freebsd.org/pipermail/freebsd-current/2017-November/067463.html
Snip: "illumos and ZoL seem to do the same."

Gold fails when output file is lying on ZFS 
https://sourceware.org/bugzilla/show_bug.cgi?id=22540

Given the wide scope of use of zfs and both syscalls across multiple OS's, and possible changes to POSIX documentation/standards, changes to the underlying fallocate/fadvise functions may also be indicated here.