Do you happen to know if this happens on F22 as well?

CC-ing Michel Normand who wrote the ppc64le backend.

The other thing to try would be increasing the stack size, since
ppc64 code often needs a lot more stack than is available by default.

Put something like:

%ifarch ppc64 ppc64le
ulimit -a
ulimit -Hs 65536
ulimit -Ss 65536
%endif

(or larger even) before the make.

yeah, the larger stack helps - http://ppc.koji.fedoraproject.org/koji/taskinfo?taskID=2182090

diff --git a/ejabberd.spec b/ejabberd.spec
index 14d374a..55a9e26 100644
--- a/ejabberd.spec
+++ b/ejabberd.spec
@@ -150,6 +150,11 @@ autoreconf -ivf
 make
 %if 0%{?_with_hevea}
 pushd doc
+%ifarch %{power64}
+ulimit -a
+ulimit -Hs 65536
+ulimit -Ss 65536
+%endif
 # remove pre-built docs
 rm -f dev.html features.html
 # See this link - http://thread.gmane.org/gmane.linux.redhat.fedora.devel/198954/focus=198957

I believe you can coalesce the two ulimit statements into just:

  ulimit -s 65536

This is not the first package we've had to do this for.  I
wonder if we can increase the default stack size on ppc64/le?
Honestly I've never seen the point of limiting stack in the
first place - we don't limit any other type of memory by default.

I have already seen also on s390(x) that the default stack was too small. Is the limit a kernel default? I think there is a relation between the default stack size and the number of available processes/thread before they get memory exhausted. But I agree maybe it is the right time to change the too low deaults.

ejabberd-14.07-6.fc21 has been submitted as an update for Fedora 21.
https://admin.fedoraproject.org/updates/ejabberd-14.07-6.fc21

I'm guessing it is a kernel default.  However the best place
to change the default might be in /etc/security/limits.conf
which is in the 'pam' package.  I'm not sure if limits.conf
applies only to logins, or to every process.

Package ejabberd-14.07-6.fc21:
* should fix your issue,
* was pushed to the Fedora 21 testing repository,
* should be available at your local mirror within two days.
Update it with:
# su -c 'yum update --enablerepo=updates-testing ejabberd-14.07-6.fc21'
as soon as you are able to.
Please go to the following url:
https://admin.fedoraproject.org/updates/FEDORA-2014-15140/ejabberd-14.07-6.fc21
then log in and leave karma (feedback).

ejabberd-14.07-6.fc21 has been pushed to the Fedora 21 stable repository.  If problems still persist, please make note of it in this bug report.